Antoine and David are 12 years old when they agree that if either one of them ever earns more than $200,000 in one year he will buy the other one a new car. After college, Antoine starts a company that provides transportation to senior citizens who cannot drive. When David reads in the newspaper that Antoine’s business has been purchased by a healthcare provider for $5 million, David believes that he is owed a new car. The agreement for the new car between Antoine and David was not a legal contract because it fails to meet which requirement(s) of a contract?