3.1Lily is a law student who has started studying contract law. One day her beloved cat, Lord Denning, was hit by a car. Lily rushed Lord Denning to the vet who performed emergency surgery that saved Lord Denning's life. The vet billed Lily $3 000. Lily was shocked, but recalled the rule that past consideration is not good consideration. She pointed out to the vet that he had already cared for her cat (past consideration) and, as Lily had made no promise to pay for that service, she was under no obligation to pay the vet.

Advise Lily. Explain why you came to this answer, stating the relevant principles in full with appropriate authorities.