Minor memo

Your senior partner, John Smith has called you in again relative to another client, Jack Harston. It turns out that Jack is 16 years old and somewhat wealthy. On a date with his girlfriend Sarah Gomez (who is 18), the two decided to purchase timeshare together in Hawaii. They located the perfect property while scouring the beaches and orally agreed to purchase the property from a Mrs. George who agreed to sell the young couple the time share for $500,000. Said arrangement subsequently was documented on a beach bar napkin with all parties with Mrs. George and Jack signing.

Later, the young couple realized that purchasing the property was a mistake as they offered way too much for the property. Mrs. George argues that the two must follow through on the contract.

1. Presuming that the napkin is a valid writing, is the contract enforceable against Jack Harston ? Why or why not?
2. Presuming that the napkin is a valid writing, is the contract enforceable against Sarah Gomez? Why or why not?
3. Presuming that the napkin was non-existent but there are witnesses that can testify as the conversations and Mrs. George admits in a letter that there was a contract, is the contract enforceable against Sarah and/or Jack? Why or why not?