Answer:
Bilateral contract.
Explanation:
Bilateral contract: It is a legally binding contract between two or more parties, wherein each party agree to fullfil the promise made to each other.
There are four elements necessary for the existence of a bilateral contract:
In the given case, Clay offers to pay Diane $50 for a golf lesson for Ewan, which they are fulfilling by agreeing to meet on Friday to exchange the cash for the lesson. Therefore, these parties have made a bilateral contract.