A new college graduate entered into an oral agreement with a freshman to lease the freshman her mini-refrigerator for a term of four years. The freshman was to pay the graduate $20 a month, of which $10 of the monthly charge was to be paid directly to the graduate's parents, in satisfaction of a debt the graduate owed her parents. While the graduate was putting the agreement into writing she accidentally failed to include the agreement to pay her parents directly. The freshman also failed to notice that the direct payment provision was missing before she signed the contract, which the graduate signed.

If the parents bring an action against the freshman, which of the following will have the greatest effect on the outcome?