Constance asks Kathy if Kathy will sell her used business book for $50. What is the status of the negotiation?
a) No offer has been made.
b) An offer has been made, but it may be revoked.
c) An offer has been made that may not be revoked.
d) A contract has been entered into.
e) A contract has been entered into, but it may be set-aside at the option of either party.