Help please, answer this correctly with the right case summaries

I. On Tuesday, September 10, John delivered a written offer to sell a house to Mary. The offer stated that \"This offer is to be left over until Thursday, 10 o' clock, September 12.\" On Wednesday, John sold the house to Jill. Lance found out about the sale to Jill and told Mary. At 8 am. Thursday, Lance acting as the agent of Mary, handed John a letter of acceptance. John had also posted an offer to sell his car to Ken . On the lSt September, John posted a revocation of his offer. The offer from John was received by Ken on the 4m September and a letter of acceptance was sent the same day. On the IO"I September, John's letter of revocation reached Ken. Both Mary and Ken are contemplating suing John and John has come to you for advice. Advise John. 2. Mark sent out two offers by letter. One to sell his boat and the other a car to Kate and Ben respectively. The cost of the boat was $3M and the car was $2.5M. Kate called Mark and told him that the boat was overpriced and she would pay him $2.8M for same. Mark refused her offer. On ending his call, Jake who was in the room with him offered to pay him $3.5M but asked him to give him until Next Fri. Mark does not answer. Kate calls him two days later to inform Mark that she will pay the $3M. Mark says yes and sells the boat to her. The following Friday, Jake comes with his money for the boat. Meanwhile, Ben thinking the car is under priced, immediately upon receiving the letter faxed his acceptance to Mark and in the letter told him that he would pick up the car next Friday. Mark sold the car on Tuesday to Paula. On Friday Ben arrived with his money and a second driver to receive the car to be told by Mark that the car was sold since he did not hear from him. Ben then informs him that he sent a fax. Mark's machine is not working. Ben tells him that he will sue him as he accepted his offer. Advise Mark