You post a notice at school that you will sell your laptop computer for $1,200. A buyer comes by your room to look at it while you are gone and your roommate sells it for $1,100, thinking you would be happy with that price, which you did not authorize.

a. you must enter into a written agreement with your roommate for it to be valid.
b. you can accept the deal by express or implied ratification.
c. the deal cannot be valid because there was no consent.
d. you must accept the deal because people living together have power of attorney