help to solve this and get positive feedback for sure

Comment on any four of the five scenarios described below. By 'comment', I mean tell me if we have a contract and why. Assume the facts as stated can be proved.... 1."I promise to give you my bicycle for $1 at 4pm today", Assume you accept. 2. "I promise to give my bicycle at 4pm today", Assume you 'accept', 3. "I promise to sell you the machine gun that my grandfather left me when he died for $60,000 cash, payable at 4pm today".. The machine gun is now on the banned weapons list established by the government, 4: You were shopping at Leon's for a new couch and the clerk, after 15 minutes of back and forth, said to you "Ok, we'll sell you the couch for 5600." You said you'd think about, left the store and returned 15 minutes later and said to the clerk "ok, I'll buy it for 5600". He replied, I just sold it." 5. You offer to sell me your car for $12,500. I think that's a pretty good price but it's more than I want to pay. "I'll give you $11,000 cash" I tell you, You respond with an abrupt "no" I then offer the full asking price of $12.500, Do we have a valid contract