Jerry orders some new gourmet food from FreshHipFood Inc. online. The food is delivered to Janice by mistake. Janice keeps the food and does not pay for it$.$ FreshHipFoodInc. can enforce Janice to pay under the theory of

a$.$

voidable contract.

b$.$

unilateral contract.

c$.$

quasi$-$contract theory.

d$.$

executed contract.