<SUBMISSION>
<ACCESSION-NUMBER>0001130464-08-000144
<TYPE>8-K
<PUBLIC-DOCUMENT-COUNT>3
<PERIOD>20080429
<ITEMS>1.01
<ITEMS>9.01
<FILING-DATE>20080430
<DATE-OF-FILING-DATE-CHANGE>20080429
<FILER>
<COMPANY-DATA>
<CONFORMED-NAME>BLACK HILLS CORP /SD/
<CIK>0001130464
<ASSIGNED-SIC>4911
<IRS-NUMBER>460458824
<STATE-OF-INCORPORATION>SD
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<FILING-VALUES>
<FORM-TYPE>8-K
<ACT>34
<FILE-NUMBER>001-31303
<FILM-NUMBER>08787385
</FILING-VALUES>
<BUSINESS-ADDRESS>
<STREET1>625 9TH STREET
<STREET2>PO BOX 1400
<CITY>RAPID CITY
<STATE>SD
<ZIP>57709
<PHONE>6057212343
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>625 9TH STREET
<STREET2>PO BOX 1400
<CITY>RAPID
<STATE>SD
<ZIP>57709
</MAIL-ADDRESS>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>BLACK HILLS HOLDING CORP
<DATE-CHANGED>20001222
</FORMER-COMPANY>
</FILER>
<DOCUMENT>
<TYPE>8-K
<SEQUENCE>1
<FILENAME>form8k_aquila-extension.htm
<DESCRIPTION>AQUILA EXTENSION
<TEXT>
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<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;border-bottom:solid 2.25pt;padding-bottom:1;'>&nbsp;</p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><font size=5>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><B><font SIZE=5>UNITED STATES</font></B></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><B><font SIZE=5>SECURITIES AND EXCHANGE COMMISSION</font></B></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><b><font size=2>Washington, D.C. 20549</font></b></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><b><font size=3>___________</font></b></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=3>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><B><font SIZE=5>FORM 8-K</font></B></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><b><font size=3>____________</font></b></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><font size=3>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><B><font SIZE=2>CURRENT REPORT</font></B></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><b><font size=2>PURSUANT TO SECTION 13 OR 15(d) OF THE</font></b></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><B><font SIZE=2>SECURITIES EXCHANGE ACT OF 1934</font></B></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><font size=3>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><b><font size=2>Date of Report (Date of earliest event reported) April 29, 2008</font></b></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><b><font size=3>____________</font></b></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><font size=3>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><B><font SIZE=5>BLACK HILLS CORPORATION</font></B></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><b><font size=2>(Exact name of registrant as specified in its charter)</font></b></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><b><font size=3>____________</font></b></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><font size=3>&nbsp;</font></p>


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        <td  colspan="4" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:center;margin-top:0pt;margin-bottom:0pt'><b><font size=2>South Dakota</font></b></p> </td> </tr>
    <tr >
        <td  colspan="4" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:center;margin-top:0pt;margin-bottom:0pt'><b><font size=2>(State or other jurisdiction of incorporation)</font></b></p> </td> </tr>
    <tr >
        <td width="162" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:center;margin-top:0pt;margin-bottom:0pt'><b><font size=2>001-31303</font></b></p> </td>
        <td width="234" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:center;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td>
        <td  colspan="2" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:center;margin-top:0pt;margin-bottom:0pt'><b><font size=2>46-0458824</font></b></p> </td> </tr>
    <tr >
        <td width="162" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:center;margin-top:0pt;margin-bottom:0pt'><b><font size=2>(Commission&nbsp;File&nbsp;Number)</font></b></p> </td>
        <td width="234" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:center;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td>
        <td  colspan="2" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:center;margin-top:0pt;margin-bottom:0pt'><b><font size=2>(IRS&nbsp;Employer&nbsp;Identification&nbsp;No.)</font></b></p> </td> </tr>
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        <td width="162" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:center;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td>
        <td width="234" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:center;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td>
        <td  colspan="2" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:center;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td> </tr>
    <tr >
        <td  colspan="2" rowspan=2 valign=top style='padding: 0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><b><font size=2>625 Ninth Street, PO Box 1400 </font></b></p>
<p style='margin-left:12.6pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><b><font size=2>Rapid City, South Dakota</font></b></p>
<p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><b><font size=2>(Address of principal executive offices)</font></b></p> </td>
        <td  colspan="2" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:center;margin-top:0pt;margin-bottom:0pt'><b><font size=2>57709-1400</font></b></p> </td> </tr>
    <tr >
        <td  colspan="2" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:center;margin-top:0pt;margin-bottom:0pt'><b><font size=2>(Zip Code)</font></b></p> </td> </tr>
    <tr >
        <td  colspan="4" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:center;margin-top:0pt;margin-bottom:0pt'><b><font size=2>605.721.1700</font></b></p> </td> </tr>
    <tr >
        <td  colspan="4" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:center;margin-top:0pt;margin-bottom:0pt'><b><font size=2>(Registrant&#146;s telephone number, including area code)</font></b></p> </td> </tr>
    <tr >
        <td width="162" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:center;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td>
        <td  colspan="2" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:center;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td>
        <td width="186" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:center;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td> </tr>
    <tr >
        <td  colspan="4" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:center;margin-top:0pt;margin-bottom:0pt'><b><font size=2>Not Applicable</font></b></p> </td> </tr>
    <tr >
        <td  colspan="4" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:center;margin-top:0pt;margin-bottom:0pt'><b><font size=2>(Former name or former address, if changed since last report)</font></b></p> </td> </tr>
    <tr>
        <td width="162" ></td>

        <td width="234" ></td>

        <td width="12" ></td>

        <td width="186" ></td> </tr> </table>
            </div>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><b><font size=3>____________</font></b></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt; text-indent:0.5in;text-align:left;'><font size=2>Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (</font><i><font size=2>see</font></i><font size=2> General Instruction A.2. below):</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>


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            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1><img src="ballot.jpg"></font></p> </td>
        <td width="452" nowrap valign=top >
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)</font></p> </td> </tr></table>
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<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>


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            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1><img src="ballot.jpg"></font></p> </td>
        <td width="452" nowrap valign=top >
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)</font></p> </td> </tr></table>
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<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>


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            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1><img src="ballot.jpg"></font></p> </td>
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            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))</font></p> </td> </tr></table>
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<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>


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            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1><img src="ballot.jpg"></font></p> </td>
        <td width="556" nowrap valign=top >
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))</font></p> </td> </tr></table>
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<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;border-bottom:solid 2.25pt;padding-bottom:1;'><font size=5>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><font size=2>1</font></p>
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            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><b><font size=2>Item 1.01</font></b></p> </td>
        <td width="316" nowrap valign=top >
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><b><font size=2>Entry into a Material Definitive Agreement</font></b></p> </td> </tr></table>
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<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:justify;'><font size=2>On February 6, 2007, we entered into agreements with Aquila, Inc. (&#147;Aquila&#148;) to acquire the gas utilities operated by Aquila in Colorado, Iowa, Kansas and Nebraska, and the electric utility operated by Aquila in Colorado, together with certain related assets, for $940 million in cash.  At the same time we entered into our agreements with Aquila, Aquila also entered into an agreement with Great Plains Energy Incorporated (&#147;Great Plains&#148;) for the merger of a subsidiary of Great Plains with and into Aquila.  Each transaction is contingent on the completion of the other transaction, meaning that one transaction will not be completed unless the other transaction is completed.</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:justify;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:justify;'><font size=2>The Agreement and Plan of Merger (&#147;Merger Agreement&#148;), the Asset Purchase Agreement (&#147;APA&#148;) and the Partnership Interests Purchase Agreement (&#147;PIPA&#148;), each dated February 6, 2007, provided they may be terminated if the transactions have not been consummated by February 6, 2008 (the &#147;Termination Date&#148;).  Each agreement further provides that if any party to the agreement determines that additional time is necessary to obtain any of the specified regulatory consents or approvals, the Termination Date may be extended from time to time by written notice, up to August 6, 2008.  Black Hills Corporation, Aquila and Great Plains previously extended the Termination Date under the agreements to May 1, 2008.</font><font size=1>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>On April 29, 2008, Black Hills Corporation, Aquila and Great Plains provided notices to each other again mutually extending the Termination Date under their APA, PIPA and Merger Agreement to August 6, 2008.</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>


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            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><b><font size=2>Item 9.01</font></b></p> </td>
        <td width="253" nowrap valign=top style='padding:5.0pt 0in 5.0pt 0in; '>
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><b><font size=2>Financial Statements and Exhibits</font></b></p> </td> </tr></table>
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        <td width="24" valign=top style='padding:5.0pt 0in 5.0pt 0in'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td>
        <td width="48" valign=top style='padding:5.0pt 0in 5.0pt 0in'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=2>(d)</font></p> </td>
        <td  valign=top style='padding:5.0pt 0in 5.0pt 0in'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=2>Exhibits</font></p> </td> </tr></table>
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            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=2>10</font></p> </td>
        <td width="577" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=2>Mutual Notice of Extension provided as of April 29, 2008, by and among Black Hills Corporation, Aquila, Inc., and Great Plains Energy Incorporated.</font></p> </td> </tr></table>
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<p style=' margin-bottom:0pt; margin-top:5pt; margin-left:0.25in;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:5pt; margin-left:1in; text-indent:-0.25in;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><font size=2>2</font></p>
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<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'>
</p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><U><font SIZE=2>SIGNATURES</font></U></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt; text-indent:0.51in;text-align:left;'><font size=2>Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>


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            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td>
        <td width="319" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font SIZE=2>BLACK HILLS CORPORATION</font></p> </td> </tr>
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        <td width="319" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td>
        <td width="319" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td> </tr>
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        <td width="319" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td>
        <td width="319" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td> </tr>
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        <td width="319" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td>
        <td width="319" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=2>By:&nbsp;</font><u><font size=2>/s/ Steven J. Helmers</font></u>                                                                                                                     </p> </td> </tr>
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            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td>
        <td width="319" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:21.0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=2>Steven J. Helmers</font></p> </td> </tr>
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            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td>
        <td width="319" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:21.75pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=2>Senior Vice President</font></p> </td> </tr>
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            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td>
        <td width="319" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:26.25pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=2>and General Counsel</font></p> </td> </tr>
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            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td>
        <td width="319" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td> </tr>
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            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=2>Date:&nbsp;&nbsp;April 29, 2008</font></p> </td>
        <td width="319" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td> </tr></table>
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<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><font size=2>3</font></p>
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<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'>
<font size=2>Exhibit Index</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:5pt; margin-top:5pt; margin-left:0.75in;text-align:left;'><font size=2>Exhibit #</font></p>


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            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=2>10</font></p> </td>
        <td width="505" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=2>Mutual Notice of Extension provided as of April 29, 2008, by and among Black Hills Corporation, Aquila, Inc., and Great Plains Energy Incorporated.</font></p> </td>
        <td width="505" valign=top style='padding:0in 5.4pt 0in 5.4pt'>
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td> </tr></table>
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<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:center;'><font size=2>4</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>
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<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>


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<p style=' margin-bottom:12pt; margin-top:0pt;text-align:center;'><B><font SIZE=2>MUTUAL NOTICE OF EXTENSION</font></B></p>

<p style=' margin-bottom:12pt; margin-top:0pt; text-indent:0.5in;text-align:left;'><font size=2>This Mutual Notice of Extension (the &#147;Notice&#148;) is provided as of April 29, 2008, by and among Black Hills Corporation, a South Dakota corporation (&#147;</font><u><font size=2>Black Hills</font></u><font size=2>&#148;), Aquila, Inc., a Delaware corporation (&#147;</font><u><font size=2>Aquila</font></u><font size=2>&#148;), and Great Plains Energy Incorporated, a Missouri corporation (&#147;</font><u><font size=2>Great Plains</font></u><font size=2>&#148;).</font></p>

<p style=' margin-bottom:12pt; margin-top:0pt;text-align:center;'><b><font size=2>Background</font></b></p>

<p style=' margin-bottom:12pt; margin-top:0pt; text-indent:0.5in;text-align:left;'><font size=2>The parties have entered into an Agreement and Plan of Merger (&#147;Merger Agreement), an Asset Purchase Agreement (&#147;APA&#148;) and a Partnership Interests Purchase Agreement (&#147;PIPA&#148;), each dated February 6, 2007.  These agreements provide that each of them may be terminated at any time prior to the Effective Time (as defined in the agreements) if, among other things, the transactions contemplated by the agreements have not been consummated by the first anniversary of the agreements (the &#147;Termination Date&#148;).  The agreements further provide that either Aquila or Great Plains may extend the Termination Date of the Merger Agreement, and either Aquila or Black Hills may extend the Termination Date of the APA and PIPA, from time to time up to a date not beyond 18 months after the dates of the agreements, if any of them determines that additional time is necessary to
obtain any of the Material Company Regulatory Consents or the Material Parent Regulatory Consents (as defined in the Merger Agreement), or the Required Regulatory Approvals (as defined in the APA and PIPA).  </font></p>

<p style=' margin-bottom:12pt; margin-top:0pt; text-indent:0.5in;text-align:left;'><font size=2>On January 31, 2008, the parties determined that additional time was necessary to obtain the Material Company Regulatory Consents, the Material Parent Regulatory Consents and the Required Regulatory Approvals, and entered into a Mutual Notice of Extension pursuant to which the Termination Dates of the Merger Agreement, APA and PIPA were initially extended to May 1, 2008.</font></p>

<p style=' margin-bottom:12pt; margin-top:0pt; text-indent:0.5in;text-align:left;'><font size=2>The parties have since determined that further time is necessary to obtain the Material Company Regulatory Consents, the Material Parent Regulatory Consents and the Required Regulatory Approvals, and each party desires to further extend the Termination Dates of the Merger Agreement, APA and PIPA.</font></p>

<p style=' margin-bottom:12pt; margin-top:0pt;text-align:center;'><b><font size=2>Mutual Notice of Extension</font></b></p>

<p style=' margin-bottom:12pt; margin-top:0pt; text-indent:0.5in;text-align:left;'><font size=2>Each of Aquila and Great Plains hereby provides written notice to the other, pursuant to Section 9.2 of the Merger Agreement, that the Termination Date, as defined in that agreement, is hereby extended to August 6, 2008. </font></p>

<p style=' margin-bottom:12pt; margin-top:0pt; text-indent:0.5in;text-align:left;'><font size=2>Each of Black Hills and Aquila hereby provides written notice to the other and to Great Plains, pursuant to Sections 10.1(b) of the APA and the PIPA, that the Termination Date, as defined in those agreements, is hereby extended to August 6, 2008.</font></p>

<p style=' margin-bottom:12pt; margin-top:0pt; text-indent:0.5in;text-align:left;'><font size=2>The parties acknowledge that if the transactions contemplated by the Merger Agreement, APA and PIPA have not been consummated on or before August 6, 2008, (i) the Board of Directors of either Aquila or Great Plains may terminate the Merger Agreement pursuant to </font></p>
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<p style=' margin-bottom:12pt; margin-top:0pt;text-align:left;'><font size=2>Section 9.1(b) thereof, and (ii) either Aquila or Black Hills may terminate the APA and PIPA pursuant to Section 10.1(b) thereof.</font></p>

<p style=' margin-bottom:12pt; margin-top:0pt;text-align:center;'><font size=2>[signature page follows]</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=1>1-LA/975924.1</font><font size=2> </font></p>
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<font size=2>IN WITNESS WHEREOF, this Mutual Notice of Extension has been duly executed and delivered by the duly authorized officers of the parties as of the date first written above.</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font SIZE=2>BLACK HILLS CORPORATION</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>By:  </font><u><font size=2>/s/ Steven J. Helmers</font></u></p>


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            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td>
        <td width="187" nowrap valign=top >
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=2>Name:  Steven J. Helmers</font></p> </td> </tr></table>
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<table border="0" cellspacing=0 cellpadding=0 width="369" style='border-collapse:collapse; '>
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            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td>
        <td width="51" nowrap valign=top >
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=2>Title:  </font></p> </td>
        <td width="299" nowrap valign=top >
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=2>Senior Vice President and General Counsel</font></p> </td> </tr></table>
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<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font SIZE=2>GREAT PLAINS ENERGY INCORPORATED</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>By:  </font><u><font size=2>/s/ Terry Bassham</font></u></p>


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<table border="0" cellspacing=0 cellpadding=0 width="195" style='border-collapse:collapse'>
    <tr >
        <td width="28" nowrap valign=top >
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td>
        <td width="167" nowrap valign=top >
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=2>Name:  Terry Bassham</font></p> </td> </tr></table>
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<table border="0" cellspacing=0 cellpadding=0 width="415" style='border-collapse:collapse; '>
    <tr >
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            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td>
        <td width="52" nowrap valign=top >
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=2>Title:</font></p> </td>
        <td width="335" nowrap valign=top >
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=2>Executive Vice President &#150; Finance and Strategic</font></p> </td> </tr></table>
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<table border="0" cellspacing=0 cellpadding=0 width="365" style='border-collapse:collapse; '>
    <tr >
        <td width="80" nowrap valign=top >
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td>
        <td width="285" nowrap valign=top >
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=2>Development and Chief Financial Officer</font></p> </td> </tr></table>
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<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font SIZE=2>AQUILA, INC.</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>By:  </font><u><font size=2>/s/ Christopher M. Reitz</font></u></p>


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<table border="0" cellspacing=0 cellpadding=0 width="229" style='border-collapse:collapse; '>
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            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td>
        <td width="201" nowrap valign=top >
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=2>Name: Christopher M. Reitz</font></p> </td> </tr></table>
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<table border="0" cellspacing=0 cellpadding=0 width="439" style='border-collapse:collapse'>
    <tr >
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            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=1>&nbsp;</font></p> </td>
        <td width="45" nowrap valign=top >
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=2>Title:  </font></p> </td>
        <td width="365" nowrap valign=top >
            <p style='margin-left:0pt;text-indent:0pt;text-align:left;margin-top:0pt;margin-bottom:0pt'><font size=2>Senior Vice President, General Counsel and Secretary</font></p> </td> </tr></table>
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<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=1>1-LA/975924.1</font><font size=2> </font></p>

<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'><font size=2>&nbsp;</font></p>
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<p style=' margin-bottom:0pt; margin-top:0pt;text-align:left;'>&nbsp;</p>


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