Restatement of Contracts,
Second §§ 71 and 81
§
71 sez that an act, forbearance, or change in a legal relation must be “sought
by the promisor in exchange for his promise and given by the promisee in
exchange for that promise” in order to constitute consideration.
§
81 sez that just because the performance isn’t the thing that induced a promise
doesn’t mean it doesn’t constitute consideration, and vice versa.