Question: Reynold Williams Jr., purchased a 2004 GMC Yukon SLT from Spitzer Autoworld Canton, L.L.C. According to the written purchase agreement, Williams was to receive a trade-in allowance of $15,500 for his 2003 Ford Explorer. The purchase agreement also had a statement indicating that this was the entire agreement between the parties. Williams subsequently sued Spitzer, stating he and Spitzer had reached a prior oral agreement that he would receive a trade-in allowance of $16,500 and that this agreement should have been incorporated in the purchase agreement. Williams stated that he had failed to notice the difference when signing the contract because he was focused on the monthly payment amount. He stated that the error only became apparent to him when he found out that his financing had been declined and that he owed an additional $2,000 to pay off the loan secured by the Explorer. How should the court rule on Williams' claim, and why?