Maurice Offered to Sell His Used Computer to Mike for $300

Maurice offered to sell his used computer to Mike for $300, and Mike accepted. Both Maurice and Mike believed that the computer was one year old. When the receipt was found, however, it was discovered that the computer was actually 18 months old. Mike wants out of the agreement based on mutual mistake. Which of the following is Maurice's best position in an attempt to enforce the contract?

A) That the mistake did not have a material effect on the agreement.
B) That the mistake should be allocated equally between the parties.
C) That a mutual mistake was involved.
D) That a unilateral mistake was involved.
E) None of these because, as a matter of law, Mike can get out of the contract with this type of mistake.