a homeowner entered into a contract with a landscaper. the contract specified that the homeowner would pay the landscaper $10,000 upon completion of a list of projects. the landscaper performed the work while the homeowner was away on vacation. when the landscaper sought payment, the homeowner refused, noting that a tree had not been trimmed as required by the contract. the landscaper responded that, since he would now have to forego other work in order to trim the tree, he would do it but only if the homeowner agreed to pay him a total of $10,500 for his services. the homeowner, desperate to have the work completed, agreed. once the work was completed, however, the homeowner gave the landscaper a check for $10,000, and refused to pay more. the landscaper sued for breach of contract. is the landscaper likely to succeed in his claim?