Harvey was playing baseball in his yard and hit a ball too far into his neighbor's yard. The ball struck a branch on a tree, causing the branch to fall and injuring Harvey's neighbor, who was standing under the tree.

Harveys neighbor initially threatens to sue Harvey, but the two agree to settle the matter out of court through an oral agreement. In particular, Harvey promises to pay $5,000 as long as the neighbor agrees not to sue him for negligence (both Harvey and his neighbor have legal capacity).

Nevertheless, Harveys neighbor sues him for negligence.

Did Harvey and his neighbor have a valid contract? Did Harveys neighbor breach the contract? Why? What remedies can Harvey seek?