Toughones, a car part manufacturer, signed a contract to license computer software from Vizera Inc. for $250,000. This software is to be used to keep track of inventory, accounts receivable, and other financial data. After the software was installed, the computer system worked, but it had a few glitches. Toughones refused to pay the full amount mentioned in the contract. To settle the dispute, the parties agree that $180,000 is to be paid as full and final payment for the software. Toughones paid $180,000 as agreed. What kind of agreement did Toughones and Vizera reach in the end?