vivian offered to buy ben's violin for $2,000 and ben accepted. three days later, vivian gave ben $2,000 in cash, and ben gave vivian possession of the violin. which of the following sets of terms best describes the contract between vivian and ben? a. bilateral, express, valid, and executed b. bilateral, implied-in-fact, valid, and partially executed c. unilateral, implied-in-fact, avoidable, and executory d. unilateral, express, avoidable, and executed
