If the original contract is still executory on both sides, either in whole or in part, and the parties in forming the new contract waive or release any liability created by the original contract, such waiver or release is a consideration for the promise of the party whose liability is thus released.1 If the original contract is subject to be terminated by the happening of a condition subsequent, and it is in whole or in part executory on both sides, the mutual discharge of liabilities under such contract is a sufficient consideration.2