Suppose that Dave was a reckless 21-year old who was, in Sam's opinion (Sam is Dave grandpa), a bit too fond of cold beer, high stakes poker, and fast cars. Sam promised to will the Thunderbird to Dave if Dave would refrain from drinking and gambling and avoid speeding tickets for the rest of Sam's life. Dave promised to refrain from drinking and gambling and to avoid speeding tickets for the rest of Sam's life.

Select the best answer and provide legal support for your selection:

1. A bilateral contract is formed. Sam must change his will.
2. A unilateral contract is formed. Sam is under no obligation to change his will.
3. A unilateral contract is formed. Sam must change his will.
4. A bilateral contract is formed. Sam is under no obligation to change his will.