Leila agrees to pay Kendrick $35,000 to repair windmills. Confident of this cash, Kendrick contracts to buy Derrick's used Porsche for $33,000. Then Leila informs Kendrick that she does not need his help and will not pay him. Kendrick tells Derrick that he no longer wants the Porsche. Derrick sues Kendrick, and Kendrick files suit against Leila. What law or laws govern each of these contracts.