Diana was selling $500 tickets to her favorite charity's fundraiser. She asked her good friend, Donna, to purchase a ticket. Donna declined, stating that she could not afford the ticket price. Diana persisted. When Donna refused to purchase a ticket, Diana declared, "If you do not buy a ticket, I will never go shopping with you again!" Fearing the loss of her shopping buddy, Donna gave in and agreed to purchase a ticket. When Diana tried to collect the $500 from Donna, Donna refused to give Diana the money. If Diana sues Donna for the price of the ticket, who will win?