George offers to sell his car to Suzy for $10,000 on the coming Sunday, to which Suzy agrees. They write down the details on a paper. On the decided day, Suzy pays the cash to George, but he refuses to sell the car to her saying that his friend Marty has offered to pay $30,000 for the same car. On the basis of which doctrine can Suzy sue George?

Quasi-contract

Partially executed contract

Executory contract

Promissory estoppel

Implied contract