Mick and Vick are negotiating the sale of Mick's car to Vick. During the negotiations, Mick says that he will throw in the metric tool set if Vick buys the car for $40,000. The two draw up an agreement and sign it. The agreement, though, says nothing about the tool set being part of the deal.

a. The parol evidence rule allows evidence of subsequent modifications and the agreement about the tool set is a subsequent modification.

b. The deal regarding the tool set is a subsequent modification and thus is not allowed under the parol evidence rule.

c. The Parol evidence rule only allows evidence regarding promises made prior to the formation of the written contract.

d. None of the above.