Answer:
The answer is: NO
Explanation:
In order for a contract to exist, consideration must be present. Consideration is the benefit bargained between the two parties in a contract. Consideration is considered the main reason of why a contract exists.
Consideration doesn't exist in this case, since Frank didn't exchange anything in order to get the $500. His boss offered the money for his past performance, but past consideration doesn't create a new contract. In the past he sold cellphones and his boss already paid him for doing so.