February 13, 2002 The Bank of New York, as trustee under the Guarantee Agreement referred to below 101 Barclay Street, 21 West New York, New York 10286 Attention: Vice President, Corporate Trust Administration Re: The Montana Power, L.L.C./Assumption of Guarantee Ladies and Gentlemen: Reference is made to the proposed merger (the "Merger") of The Montana Power Company, a Montana corporation ("MPC"), with and into The Montana Power, L.L.C., a Montana limited liability company ("MPC LLC"), which Merger is expected to be completed on or about the date hereof. Reference is further made to the Guarantee Agreement, dated as of November 1, 1996, between MPC and The Bank of New York as trustee. Effective upon consummation of the Merger, MPC LLC hereby assumes and agrees to be bound by all of the guarantees, covenants and agreements on the part of MPC to be performed or observed under the Guarantee Agreement as successor to MPC under such agreement. THE MONTANA POWER, L.L.C. By: /s/ Patrick T. Fleming ---------------------------- Name: Patrick T. Fleming Title: V.P., General Counsel & Secretary