Same facts as in Question 3, but Barney called Betty on March 10. He said that if Betty would keep the offer open until March 15, Barney would pay Betty $50. Betty agreed and Barney delivered to Betty a cash payment of $50. Betty called Barney on March 14 and revoked the offer to sell him the car. Betty then sold the car to Dino. Barney sued Betty for breach of contract. In whose favor should the court rule and why?