Problem
Jett drops by Mack's house and finds him working on his old Cadillac in the driveway. Mack kicks the Cadillac and exclaims to Jett, "This piece of junk isn't worth a tank of gas - you can have it." Jett says thanks and the next day comes by with his SUV to tow away the Cadillac. Mack stops him and says the Cadillac is working now. Jett goes to court and claims that the Cadillac Mack promised him was worth $2,500 and Mack should pay him that amount.
Is there a valid contract? Why or why not?
Sam puts an ad in the newspaper stating that she wants to sell her alpaca for $500. Angela goes to Sam's home and tells her that she is interested in buying the alpaca. After petting it and inspecting its feet, Angela hands Sam $500 in cash, which Sam puts in her pocket. Just then, Steve drives up and tells Sam that he'll give her $600 for the alpaca. Sam hands Angela back her $500 and sells the alpaca to Steve. Because she needs the alpaca for her sweater business, Angela sues Sam for breach of contract.
Is there a valid contract? Why or why not?