Answer:
b. Mary's counteroffer terminates Carl's offer of $1,500.
Explanation:
A counteroffer is a response made after receiving an initial offer, thereby rejecting the initial offer and replacing it with another one. Therefore the person giving the initial offer either accepts the counter offer, reject it or make another offer. The counteroffer may be greater or lesser than the original offer. In a negotiation, they can be unlimited number of counteroffers.