PC Contractors, Inc., was an excavating business in Kansas City, Missouri. Union Bank made loans to PC, subject to a perfected security interest in its equipment and other assets, including “after-acquired property.” In late 1997, PC leased heavy construction equipment from Dean Machinery Co. The lease agreements required monthly payments, which PC often made late or missed completely. After eighteen months, Dean demanded that PC either return the equipment or buy it. While attempting to obtain financing for the purchase, PC continued to make monthly payments. In November 2000, Dean, which had not filed a financing statement to cover the transaction, demanded full payment of the amount due. Before paying the price, PC went out of business and surrendered its assets to Union, which prepared to sell them. Dean filed a suit in a Missouri state court against Union to recover the equipment, claiming, in part, that the bank’s security interest had not attached to the equipment because PC had not paid for it. In whose favor should the court rule, and why?