Answer:
Correct answer is a, there is a contract for the sale of computer with the carrying case
Step-by-step explanation:
There is a contract between John and Mary to sell the laptop computer with the carrying case. Mary's counter offer to buy the laptop computer if the carrying case is included is indirectly accepted by John by replying "sold". That only means there is a meeting of minds between the two contracting parties the seller (John) and the buyer who counter offered (Mary) to sell the laptop computer with the carrying case.