                               Power of Attorney


KNOW ALL MEN BY THESE PRESENTS, that I, Lee S. Ainslie III, hereby make,
constitute and appoint John T. McCafferty as my agent and attorney-in-fact for
the purpose of executing all documents to be filed with or delivered to any
foreign or domestic governmental or regulatory body or other person pursuant to
any legal or regulatory requirement relating to the issuance, acquisition,
ownership, management or disposition of securities or investments, including all
documents required to be filed with the United States Securities and Exchange
Commission pursuant to Section 16 of the Securities Exchange Act of 1934, either
(i) in my personal capacity or (ii) in my capacity as manager or other officer
or representative of Maverick Capital Management, LLC, Maverick Capital, Ltd. or
any affiliate of either.

All past acts of the attorney-in-fact in furtherance of the foregoing are hereby
ratified and confirmed.

This power of attorney shall be valid from the date hereof until revoked by me.

IN WITNESS WHEREOF, I have executed this instrument as of the 13th day of June,
2006.



                                                     /s/ Lee S. Ainslie III
                                                     ----------------------
                                                     Lee S. Ainslie III
