1. What are the essential elements necessary to form a valid contract? Provide examples of each. 2. Under what conditions can contractual duties be modified? When does promissory estoppels apply? Provide an example. 3. What are the differences between a void contract and a voidable contract? Provide examples. 4. Which party or parties to a voidable contract have the right to disaffirm the contract? 5. Can written agreements be modified orally? Explain why or why not.