David wanted to purchase a car. He found a 1998 Volvo station-wagon and decided that it would be perfect. David rang the number in the advertisement and spoke to Sarah, the Volvo's owner.

Consider the following separate and unrelated scenarios:

(a) After some negotiations, Sarah offers to sell David the car for $14,500 and says she will keep her offer open for the next 30 minutes. Five minutes later, while David was considering the offer, Sarah receives a call from Angelo who offers $15,500 for the car. She immediately accepts Angelo's offer. David calls a few minutes later (within the 30-minute limit) and he informs Sarah that he accepts the offer, wants the car and will sue her for breach of contract.

(b) After some negotiations, Sarah offers to sell David the car for $14,500. In response, David says "I need some time to think about it. I'll call you back soon." David calls back and offers Sarah $14,000 for the car. Sarah says it is not enough. David then says "Ok. I was just seeing if I could knock you down a bit. I'll take it for $14,500." Sarah says, "No, you won't, you creep" and refuses to sell. Advise David whether he has a contract with Sarah.

(c) After some negotiations, Sarah offers to sell David the car for $14,500. David hesitates and says he will contact her by 5.00pm Friday. She agrees to keep the offer open until that time. At 4.00pm on Friday, David sends an email accepting the offer. Sarah does not open her emails until the following morning and it is only then that she sees David's acceptance. Unfortunately, she sold the car the previous day at 6.00pm. Advise David.