12) Marvin offers to sell his old computer to Harold for $800.00. Harold really wants to buy the computer, but he doesn't know if he can come up with the money. Harold asks Marvin IF Marvin would give Harold 3 days to think about the offer and try to gather the money?? Marvin agrees, so long as Harold pays Marvin $100.00 to keep the offer open for 3 days. Harold gives Marvin $100.00 to keep the offer open for 3 days. Marvin keeps the offer open for 3 days. What type of contract is this called, if any