In 1995, Bulk Petroleum Corp. (Bulk) (defendant) entered a six-year agreement to lease gasoline equipment from IFC Credit Corp. (IFC) (plaintiff). Bulk had the option to purchase the equipment at the end of the lease, with the purchase price to be determined at that time. About two weeks later, IFC assigned the lease to Finova Capital Corp. (Finova). In 2000, IFC and Bulk began negotiating Bulk’s purchase of the equipment. The parties could not agree on a price. Soon after, Finova notified Bulk that all correspondence about the purchase should go to IFC and filed for bankruptcy. In 2001, three days before the lease’s termination, Bulk sent a letter and a check to Finova. The letter stated that the check constituted “payment in full of the lease and the purchase option,” and that “[a]cceptance of this check represents full satisfaction of the obligation of Bulk . . . to Finova.” IFC received the letter and check within four days. IFC kept the check but claimed that it was only partial payment. IFC sued Bulk, seeking additional payments under the lease. The district court granted Bulk summary judgment. IFC appealed.