Graves was struck by a car driven by Koons. They then had a dispute as to whether or not the accident was Koons’s fault and as to the extent of Graves’s injuries. They finally agreed that Koons would pay Graves $ 1,500 ( and he did) in return for Graves’s promise to release Koons of all liability. In the event that Graves’s actual damages later turn out to be in excess of $ 1,500, is Graves still bound by his promise of release?