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Fair Value Measurements | 3 Months Ended
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Mar. 31, 2024
Fair Value Measurements | FAIR VALUE MEASUREMENTS Fair Value of Financial Instruments - The carrying amounts of current assets and current liabilities approximate fair value because of the short maturity of such financial instruments. Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions):
Alliant Energy | March 31, 2024 |  | December 31, 2023
|  |  | Fair Value |  |  |  | Fair Value
| Carrying |  | Level |  | Level |  | Level |  |  |  | Carrying |  | Level |  | Level |  | Level |  |
| Amount |  | 1 |  | 2 |  | 3 |  | Total |  | Amount |  | 1 |  | 2 |  | 3 |  | Total
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Money market fund investments | $10 |  |  | $10 |  |  | $— |  |  | $— |  |  | $10 |  |  | $45 |  |  | $45 |  |  | $— |  |  | $— |  |  | $45 |
Commodity derivatives | 56 |  |  | — |  |  | 46 |  |  | 10 |  |  | 56 |  |  | 88 |  |  | — |  |  | 59 |  |  | 29 |  |  | 88 |
Interest rate derivatives | 3 |  |  | — |  |  | 3 |  |  | — |  |  | 3 |  |  | 1 |  |  | — |  |  | 1 |  |  | — |  |  | 1 |
Deferred proceeds | 184 |  |  | — |  |  | — |  |  | 184 |  |  | 184 |  |  | 216 |  |  | — |  |  | — |  |  | 216 |  |  | 216 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commodity derivatives | 94 |  |  | — |  |  | 91 |  |  | 3 |  |  | 94 |  |  | 98 |  |  | — |  |  | 93 |  |  | 5 |  |  | 98 |
Long-term debt (incl. current maturities) | 9,333 |  |  | — |  |  | 9,051 |  |  | — |  |  | 9,051 |  |  | 9,034 |  |  | — |  |  | 8,677 |  |  | — |  |  | 8,677 |
IPL | March 31, 2024 |  | December 31, 2023
|  |  | Fair Value |  |  |  | Fair Value
| Carrying |  | Level |  | Level |  | Level |  |  |  | Carrying |  | Level |  | Level |  | Level |  |
| Amount |  | 1 |  | 2 |  | 3 |  | Total |  | Amount |  | 1 |  | 2 |  | 3 |  | Total
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Money market fund investments | $6 |  |  | $6 |  |  | $— |  |  | $— |  |  | $6 |  |  | $45 |  |  | $45 |  |  | $— |  |  | $— |  |  | $45 |
Commodity derivatives | 34 |  |  | — |  |  | 26 |  |  | 8 |  |  | 34 |  |  | 54 |  |  | — |  |  | 30 |  |  | 24 |  |  | 54 |
Deferred proceeds | 184 |  |  | — |  |  | — |  |  | 184 |  |  | 184 |  |  | 216 |  |  | — |  |  | — |  |  | 216 |  |  | 216 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commodity derivatives | 30 |  |  | — |  |  | 27 |  |  | 3 |  |  | 30 |  |  | 30 |  |  | — |  |  | 25 |  |  | 5 |  |  | 30 |
Long-term debt (incl. current maturities) | 3,945 |  |  | — |  |  | 3,607 |  |  | — |  |  | 3,607 |  |  | 3,945 |  |  | — |  |  | 3,664 |  |  | — |  |  | 3,664 |
WPL | March 31, 2024 |  | December 31, 2023
|  |  | Fair Value |  |  |  | Fair Value
| Carrying |  | Level |  | Level |  | Level |  |  |  | Carrying |  | Level |  | Level |  | Level |  |
| Amount |  | 1 |  | 2 |  | 3 |  | Total |  | Amount |  | 1 |  | 2 |  | 3 |  | Total
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commodity derivatives | $22 |  |  | $— |  |  | $20 |  |  | $2 |  |  | $22 |  |  | $34 |  |  | $— |  |  | $29 |  |  | $5 |  |  | $34 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commodity derivatives | 64 |  |  | — |  |  | 64 |  |  | — |  |  | 64 |  |  | 68 |  |  | — |  |  | 68 |  |  | — |  |  | 68 |
Long-term debt | 3,367 |  |  | — |  |  | 3,176 |  |  | — |  |  | 3,176 |  |  | 3,070 |  |  | — |  |  | 2,933 |  |  | — |  |  | 2,933 |
Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions):
Alliant Energy | Commodity Contract Derivative |  |
| Assets and (Liabilities), net |  | Deferred Proceeds
Three Months Ended March 31 | 2024 |  | 2023 |  | 2024 |  | 2023
Beginning balance, January 1 | $24 |  | $19 |  | $216 |  | $185
Total net losses included in changes in net assets (realized/unrealized) | (3) |  | (4) |  | — |  | —
Settlements (a) | (14) |  | (20) |  | (32) |  | (32)
Ending balance, March 31 | $7 |  | ($5) |  | $184 |  | $153
The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at March 31 | ($3) |  | ($4) |  | $— |  | $—
IPL | Commodity Contract Derivative |  |
| Assets and (Liabilities), net |  | Deferred Proceeds
Three Months Ended March 31 | 2024 |  | 2023 |  | 2024 |  | 2023
Beginning balance, January 1 | $19 |  | $16 |  | $216 |  | $185
Total net gains (losses) included in changes in net assets (realized/unrealized) | (4) |  | 1 |  | — |  | —
Settlements (a) | (10) |  | (17) |  | (32) |  | (32)
Ending balance, March 31 | $5 |  | $— |  | $184 |  | $153
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31 | ($4) |  | $1 |  | $— |  | $—
WPL | Commodity Contract Derivative
| Assets and (Liabilities), net
Three Months Ended March 31 | 2024 |  | 2023
Beginning balance, January 1 | $5 |  | $3
Total net gains (losses) included in changes in net assets (realized/unrealized) | 1 |  | (5)
Settlements | (4) |  | (3)
Ending balance, March 31 | $2 |  | ($5)
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31 | $1 |  | ($5)
(a)Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for expected credit losses associated with the receivables sold and cash amounts received from the receivables sold. Commodity Contracts - The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets (liabilities) as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| Excluding FTRs |  | FTRs |  | Excluding FTRs |  | FTRs |  | Excluding FTRs |  | FTRs
March 31, 2024 | ($1) |  | $8 |  | ($1) |  | $6 |  | $— |  | $2
December 31, 2023 | 3 |  | 21 |  | 3 |  | 16 |  | — |  | 5
IPL [Member] |
Fair Value Measurements | FAIR VALUE MEASUREMENTS Fair Value of Financial Instruments - The carrying amounts of current assets and current liabilities approximate fair value because of the short maturity of such financial instruments. Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions):
Alliant Energy | March 31, 2024 |  | December 31, 2023
|  |  | Fair Value |  |  |  | Fair Value
| Carrying |  | Level |  | Level |  | Level |  |  |  | Carrying |  | Level |  | Level |  | Level |  |
| Amount |  | 1 |  | 2 |  | 3 |  | Total |  | Amount |  | 1 |  | 2 |  | 3 |  | Total
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Money market fund investments | $10 |  |  | $10 |  |  | $— |  |  | $— |  |  | $10 |  |  | $45 |  |  | $45 |  |  | $— |  |  | $— |  |  | $45 |
Commodity derivatives | 56 |  |  | — |  |  | 46 |  |  | 10 |  |  | 56 |  |  | 88 |  |  | — |  |  | 59 |  |  | 29 |  |  | 88 |
Interest rate derivatives | 3 |  |  | — |  |  | 3 |  |  | — |  |  | 3 |  |  | 1 |  |  | — |  |  | 1 |  |  | — |  |  | 1 |
Deferred proceeds | 184 |  |  | — |  |  | — |  |  | 184 |  |  | 184 |  |  | 216 |  |  | — |  |  | — |  |  | 216 |  |  | 216 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commodity derivatives | 94 |  |  | — |  |  | 91 |  |  | 3 |  |  | 94 |  |  | 98 |  |  | — |  |  | 93 |  |  | 5 |  |  | 98 |
Long-term debt (incl. current maturities) | 9,333 |  |  | — |  |  | 9,051 |  |  | — |  |  | 9,051 |  |  | 9,034 |  |  | — |  |  | 8,677 |  |  | — |  |  | 8,677 |
IPL | March 31, 2024 |  | December 31, 2023
|  |  | Fair Value |  |  |  | Fair Value
| Carrying |  | Level |  | Level |  | Level |  |  |  | Carrying |  | Level |  | Level |  | Level |  |
| Amount |  | 1 |  | 2 |  | 3 |  | Total |  | Amount |  | 1 |  | 2 |  | 3 |  | Total
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Money market fund investments | $6 |  |  | $6 |  |  | $— |  |  | $— |  |  | $6 |  |  | $45 |  |  | $45 |  |  | $— |  |  | $— |  |  | $45 |
Commodity derivatives | 34 |  |  | — |  |  | 26 |  |  | 8 |  |  | 34 |  |  | 54 |  |  | — |  |  | 30 |  |  | 24 |  |  | 54 |
Deferred proceeds | 184 |  |  | — |  |  | — |  |  | 184 |  |  | 184 |  |  | 216 |  |  | — |  |  | — |  |  | 216 |  |  | 216 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commodity derivatives | 30 |  |  | — |  |  | 27 |  |  | 3 |  |  | 30 |  |  | 30 |  |  | — |  |  | 25 |  |  | 5 |  |  | 30 |
Long-term debt (incl. current maturities) | 3,945 |  |  | — |  |  | 3,607 |  |  | — |  |  | 3,607 |  |  | 3,945 |  |  | — |  |  | 3,664 |  |  | — |  |  | 3,664 |
WPL | March 31, 2024 |  | December 31, 2023
|  |  | Fair Value |  |  |  | Fair Value
| Carrying |  | Level |  | Level |  | Level |  |  |  | Carrying |  | Level |  | Level |  | Level |  |
| Amount |  | 1 |  | 2 |  | 3 |  | Total |  | Amount |  | 1 |  | 2 |  | 3 |  | Total
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commodity derivatives | $22 |  |  | $— |  |  | $20 |  |  | $2 |  |  | $22 |  |  | $34 |  |  | $— |  |  | $29 |  |  | $5 |  |  | $34 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commodity derivatives | 64 |  |  | — |  |  | 64 |  |  | — |  |  | 64 |  |  | 68 |  |  | — |  |  | 68 |  |  | — |  |  | 68 |
Long-term debt | 3,367 |  |  | — |  |  | 3,176 |  |  | — |  |  | 3,176 |  |  | 3,070 |  |  | — |  |  | 2,933 |  |  | — |  |  | 2,933 |
Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions):
Alliant Energy | Commodity Contract Derivative |  |
| Assets and (Liabilities), net |  | Deferred Proceeds
Three Months Ended March 31 | 2024 |  | 2023 |  | 2024 |  | 2023
Beginning balance, January 1 | $24 |  | $19 |  | $216 |  | $185
Total net losses included in changes in net assets (realized/unrealized) | (3) |  | (4) |  | — |  | —
Settlements (a) | (14) |  | (20) |  | (32) |  | (32)
Ending balance, March 31 | $7 |  | ($5) |  | $184 |  | $153
The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at March 31 | ($3) |  | ($4) |  | $— |  | $—
IPL | Commodity Contract Derivative |  |
| Assets and (Liabilities), net |  | Deferred Proceeds
Three Months Ended March 31 | 2024 |  | 2023 |  | 2024 |  | 2023
Beginning balance, January 1 | $19 |  | $16 |  | $216 |  | $185
Total net gains (losses) included in changes in net assets (realized/unrealized) | (4) |  | 1 |  | — |  | —
Settlements (a) | (10) |  | (17) |  | (32) |  | (32)
Ending balance, March 31 | $5 |  | $— |  | $184 |  | $153
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31 | ($4) |  | $1 |  | $— |  | $—
WPL | Commodity Contract Derivative
| Assets and (Liabilities), net
Three Months Ended March 31 | 2024 |  | 2023
Beginning balance, January 1 | $5 |  | $3
Total net gains (losses) included in changes in net assets (realized/unrealized) | 1 |  | (5)
Settlements | (4) |  | (3)
Ending balance, March 31 | $2 |  | ($5)
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31 | $1 |  | ($5)
(a)Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for expected credit losses associated with the receivables sold and cash amounts received from the receivables sold. Commodity Contracts - The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets (liabilities) as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| Excluding FTRs |  | FTRs |  | Excluding FTRs |  | FTRs |  | Excluding FTRs |  | FTRs
March 31, 2024 | ($1) |  | $8 |  | ($1) |  | $6 |  | $— |  | $2
December 31, 2023 | 3 |  | 21 |  | 3 |  | 16 |  | — |  | 5
WPL [Member] |
Fair Value Measurements | FAIR VALUE MEASUREMENTS Fair Value of Financial Instruments - The carrying amounts of current assets and current liabilities approximate fair value because of the short maturity of such financial instruments. Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions):
Alliant Energy | March 31, 2024 |  | December 31, 2023
|  |  | Fair Value |  |  |  | Fair Value
| Carrying |  | Level |  | Level |  | Level |  |  |  | Carrying |  | Level |  | Level |  | Level |  |
| Amount |  | 1 |  | 2 |  | 3 |  | Total |  | Amount |  | 1 |  | 2 |  | 3 |  | Total
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Money market fund investments | $10 |  |  | $10 |  |  | $— |  |  | $— |  |  | $10 |  |  | $45 |  |  | $45 |  |  | $— |  |  | $— |  |  | $45 |
Commodity derivatives | 56 |  |  | — |  |  | 46 |  |  | 10 |  |  | 56 |  |  | 88 |  |  | — |  |  | 59 |  |  | 29 |  |  | 88 |
Interest rate derivatives | 3 |  |  | — |  |  | 3 |  |  | — |  |  | 3 |  |  | 1 |  |  | — |  |  | 1 |  |  | — |  |  | 1 |
Deferred proceeds | 184 |  |  | — |  |  | — |  |  | 184 |  |  | 184 |  |  | 216 |  |  | — |  |  | — |  |  | 216 |  |  | 216 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commodity derivatives | 94 |  |  | — |  |  | 91 |  |  | 3 |  |  | 94 |  |  | 98 |  |  | — |  |  | 93 |  |  | 5 |  |  | 98 |
Long-term debt (incl. current maturities) | 9,333 |  |  | — |  |  | 9,051 |  |  | — |  |  | 9,051 |  |  | 9,034 |  |  | — |  |  | 8,677 |  |  | — |  |  | 8,677 |
IPL | March 31, 2024 |  | December 31, 2023
|  |  | Fair Value |  |  |  | Fair Value
| Carrying |  | Level |  | Level |  | Level |  |  |  | Carrying |  | Level |  | Level |  | Level |  |
| Amount |  | 1 |  | 2 |  | 3 |  | Total |  | Amount |  | 1 |  | 2 |  | 3 |  | Total
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Money market fund investments | $6 |  |  | $6 |  |  | $— |  |  | $— |  |  | $6 |  |  | $45 |  |  | $45 |  |  | $— |  |  | $— |  |  | $45 |
Commodity derivatives | 34 |  |  | — |  |  | 26 |  |  | 8 |  |  | 34 |  |  | 54 |  |  | — |  |  | 30 |  |  | 24 |  |  | 54 |
Deferred proceeds | 184 |  |  | — |  |  | — |  |  | 184 |  |  | 184 |  |  | 216 |  |  | — |  |  | — |  |  | 216 |  |  | 216 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commodity derivatives | 30 |  |  | — |  |  | 27 |  |  | 3 |  |  | 30 |  |  | 30 |  |  | — |  |  | 25 |  |  | 5 |  |  | 30 |
Long-term debt (incl. current maturities) | 3,945 |  |  | — |  |  | 3,607 |  |  | — |  |  | 3,607 |  |  | 3,945 |  |  | — |  |  | 3,664 |  |  | — |  |  | 3,664 |
WPL | March 31, 2024 |  | December 31, 2023
|  |  | Fair Value |  |  |  | Fair Value
| Carrying |  | Level |  | Level |  | Level |  |  |  | Carrying |  | Level |  | Level |  | Level |  |
| Amount |  | 1 |  | 2 |  | 3 |  | Total |  | Amount |  | 1 |  | 2 |  | 3 |  | Total
Assets: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commodity derivatives | $22 |  |  | $— |  |  | $20 |  |  | $2 |  |  | $22 |  |  | $34 |  |  | $— |  |  | $29 |  |  | $5 |  |  | $34 |
Liabilities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commodity derivatives | 64 |  |  | — |  |  | 64 |  |  | — |  |  | 64 |  |  | 68 |  |  | — |  |  | 68 |  |  | — |  |  | 68 |
Long-term debt | 3,367 |  |  | — |  |  | 3,176 |  |  | — |  |  | 3,176 |  |  | 3,070 |  |  | — |  |  | 2,933 |  |  | — |  |  | 2,933 |
Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions):
Alliant Energy | Commodity Contract Derivative |  |
| Assets and (Liabilities), net |  | Deferred Proceeds
Three Months Ended March 31 | 2024 |  | 2023 |  | 2024 |  | 2023
Beginning balance, January 1 | $24 |  | $19 |  | $216 |  | $185
Total net losses included in changes in net assets (realized/unrealized) | (3) |  | (4) |  | — |  | —
Settlements (a) | (14) |  | (20) |  | (32) |  | (32)
Ending balance, March 31 | $7 |  | ($5) |  | $184 |  | $153
The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at March 31 | ($3) |  | ($4) |  | $— |  | $—
IPL | Commodity Contract Derivative |  |
| Assets and (Liabilities), net |  | Deferred Proceeds
Three Months Ended March 31 | 2024 |  | 2023 |  | 2024 |  | 2023
Beginning balance, January 1 | $19 |  | $16 |  | $216 |  | $185
Total net gains (losses) included in changes in net assets (realized/unrealized) | (4) |  | 1 |  | — |  | —
Settlements (a) | (10) |  | (17) |  | (32) |  | (32)
Ending balance, March 31 | $5 |  | $— |  | $184 |  | $153
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31 | ($4) |  | $1 |  | $— |  | $—
WPL | Commodity Contract Derivative
| Assets and (Liabilities), net
Three Months Ended March 31 | 2024 |  | 2023
Beginning balance, January 1 | $5 |  | $3
Total net gains (losses) included in changes in net assets (realized/unrealized) | 1 |  | (5)
Settlements | (4) |  | (3)
Ending balance, March 31 | $2 |  | ($5)
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31 | $1 |  | ($5)
(a)Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for expected credit losses associated with the receivables sold and cash amounts received from the receivables sold. Commodity Contracts - The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets (liabilities) as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| Excluding FTRs |  | FTRs |  | Excluding FTRs |  | FTRs |  | Excluding FTRs |  | FTRs
March 31, 2024 | ($1) |  | $8 |  | ($1) |  | $6 |  | $— |  | $2
December 31, 2023 | 3 |  | 21 |  | 3 |  | 16 |  | — |  | 5

X
- Definition The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482106/820-10-50-2 + Details
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