MUTUAL NOTICE OF EXTENSION
This Mutual Notice of Extension (the “Notice”) is provided as of January 31, 2008, by and among Black
Hills Corporation, a South Dakota corporation (“ Black Hills ”), Aquila, Inc., a Delaware corporation (“ Aquila
”), and Great Plains Energy Incorporated, a Missouri corporation (“ Great Plains ”).
The parties have entered into an Agreement and Plan of Merger (“Merger Agreement), an Asset
Purchase Agreement (“APA”) and a Partnership Interests Purchase Agreement (“PIPA”), 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 “Termination Date”). 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).
Each of the parties has determined that additional time is necessary to obtain the Material Company
Regulatory Consents, the Material Parent Regulatory Consents and the Required Regulatory Approvals, and
each desires to initially extend the Termination Dates of the Merger Agreement, APA and PIPA.
Mutual Notice of Extension
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 initially extended to
May 1, 2008.