Asa has a contract with Phil to personally provide fortune-telling services at Phil's daughter's birthday party. Phil's daughter decides she does not want to have a fortune teller at her birthday party, so Phil tries to assign the right to Asa's services to his neighbor, Steve. Steve:

a. can enforce the contract with Asa because Phil has assigned the rights to him.
b. can enforce the contract with Asa only if there is written documentation of Phil assigning the rights to Steve.
c. can enforce the contract with Asa only if he pays double the originally agreed price.
d. cannot enforce the contract with Asa, because rights to receive personal services cannot be assigned.