$($A$)$ Billy is correct because he had validly delegated that duty to Richard.

Billy is incorrect because the job was a personal service, and he had no right to assign either rights or duties under the contract.

Billy is incorrect, but only because the job was for under $$1,000.$

Billy is correct, but only because Richard had properly painted the house and was, therefore, responsible for the remaining duties. If Richard had improffryly painted the house, Billy would have been responsible for the remaining duties.

Billy is incorrect because his delegation did not affect his obligation to Jan.