Answer:
Hazel will have to pay Jill $750 for his remaining life because Hazel had received something which is very expensive in return in compensation of his lifetime monthly payments of $750 to Jill. So this means that the 100% contract is enforceable.
The contract formation can be proved in the court because when Hazel will say that the contract is not written so according to Statute of Fraud he is not liable to pay Jill. This means he is agreeing at the point that the contract was in place.