Answer:Mary wins because Melissa failed to object to the merchant's confirmation memorandum.
Explanation:
A contract is first establish based on offer and acceptance between two parties. The telephone conversation of Mellisa to Mary constitute a valid offer and the email communication of Mary constitute a valid acceptance.
Furthermore the time interval between the email communication and delivery of the goods are enough period for Mellisa to counter the acceptance memorandum of Mary which she failed to carry out. This is the reason Mary wins.