The correct answer is: (A) The contractor, because the oral modification is enforceable.

The oral modification of the original contract between the two parties is enforceable, because it is supported by bilateral consideration (each party agreed to accept a lesser performance from the other) and because a written contract may be modified by an oral agreement. Therefore, this is the correct answer.

(B) Incorrect. The contractor, because the court can determine the value of his services in quantum meruit.

It is true that the court could determine the value of the contractor's services in quantum meruit. However, this answer describes a potential remedy (paying for the value of the services when there is no valid contract amount) rather than a basis for liability. Therefore, this is not the best answer.

(C) Incorrect. The cafe owner, because the oral modification is unenforceable pursuant to the Statute of Frauds.

The subject of the contract between the parties is the construction of a building on land owned by the cafe owner. Even though building materials are involved, this is primarily a service contract because the services are its predominant purpose. It is therefore not covered by the Statute of Frauds. Because the contract itself is not subject to the Statute of Frauds (despite its being in writing), a modification of the contract is also not subject to the Statute of Frauds and will be valid even if not written. Thus, this answer is incorrect.

(D) Incorrect. The cafe owner, because the oral modification is unenforceable pursuant to the parol evidence rule.

An integrated writing is an agreement that the parties specify is the entirety of their agreement on a subject. The parol evidence rule precludes introduction into evidence of a prior or contemporaneous oral agreement that varies from or contradicts the terms of an integrated writing. However, it does not apply to an agreement entered into after the integrated agreement is formed. Because the oral modification at issue was entered into after the written contract for construction of the cafe was executed, the parol evidence rule does not exclude the oral agreement. Thus, this answer is incorrect.