An act which has already been performed before an act or promise is given in return is not usually sufficient as consideration. But it will be where: A A person performs a service at another's request and is later promised payment. B A person spends money on his own initiative and another party later agrees in writing to repay it. C A debt has become statute-barred but the debtor verbally acknowledges its existence. D A promissory note is given in settlement of an existing debt.