Answer: unenforceable, because it is not a bargained-for exchange.
Explanation: In simple words, an agreement will be considered as a contract only when there is a bargain of exchange. Bargain of exchange refers to the provision in which both the parties involved in a contract promises to perform an activity in exchange for one another.
In the given case, there is only one party performing something for the other. Hence it is not a contract and thus not enforceable.
