Applying the theory of contract law, discuss if these 4 situations have formed an enforceable contract. When answering 'why', give analysis based on the law.

1.) George sends Bill a letter offering to paint Bills house for $800. The letter says: You must accept by mail within three days of the date of this letter. On the second day Bill phones George to accept. Contract or not contract? Why?

2.) Mark puts an ad in the newspaper stating that he wants to sell his truck for $500. John goes to Marks home and after looking at it, John hands Mark $500 in cash, which Mark puts in his pocket. Just then, Dave drives up and tells Mark that he will give him $600 for the truck. Mark hands John back his $500 and sells the truck to Dave. Who has formed an enforceable contract? Why? Did Mark breach a contract? Why?

3.) Susan: I will sell you my laptop for $500. Jenny: No, I dont want it for $500, but Ill give you $400 for it. Susan: No way, it's like brand new! Jenny: Ok, Ill take it for $500. Do Susan and Jenny have a contract or not? Why?

4.) Lynn's cat is missing in her neighborhood. She posts a sign with a picture that states: "$50 reward for finding Lucy". Lynn asks her friend James to walk around with her and look for Lucy. He agrees. After about 40 minutes, a stranger approaches Lynn and James with Lucy the cat and asks them if they know who she belongs to. Who does Lynn owe the reward money to and why?