You Post a Notice at School That You Will Sell

You post a notice at school that you will sell your laptop computer for $600. A buyer comes by your room to look at it while you are gone and your roommate sells it for $500, thinking you would be happy with that price, which you did not authorize.

A) you must accept the deal because your roommate had implied authority
B) you must accept the deal because people living together have power of attorney
C) the deal cannot be valid because there was no consent
D) you can accept the deal by express ratification only
E) none of the other choices