Final answer:
There is a contract because at some point in time Mary was willing to sell and Mr. Jones was willing to buy the computer system for $1500.
Step-by-step explanation:
The correct answer is D) There is a contract because at some point in time Mary was willing to sell and Mr. Jones was willing to buy the computer system for $1500.
In this scenario, Mary initially advertised her old computer system for sale for $1500. Although Mr. Jones offered a lower price, Mary rejected his offers and held firm on her asking price. Despite her initial withdrawal of the offer, Mr. Jones accepted her final offer of $1500. This sequence of events demonstrates that both parties intended to enter into a contract for the sale of the computer system at the agreed-upon price.