(1986) (relying on section 45(1) and comment a). 24 . See e.g., United States R.R. Ret. Bd. v. Fritz, 449 U.S. 166, 174 (1980) (“railroad [retirement] benefits are not contractual and may be altered or even eliminated at any time”); Devlin v. Transportation Communications Int’l Union, 173 F.3d 94, 103 (2nd Cir. 1999) (a claim to vested welfare benefits is contradicted by the ... unambiguous reservation in the plan documents of its right to amend the plan”); International Union, United Auto., Aerospace and Agric. Implement Workers of Amer. v. BVR Liquidating Inc., 190 F.3d 768, 773 (6th Cir. 1999) (“the inclusion of a ‘reservation of rights’ provision establishes that there was no intent for benefits to vest”); McGrath v. Rhode Island Retirement Bd., 88 F.3d 12, 17-18 (1st Cir. 1998) (<HOLDING>); In re Unisys Corp. Retiree Medical Benefit
holding that performance of employment services constituted acceptance of the offer of participation in bonus plan and a binding unilateral contract was thereby formed recognizing that generally    with supposed unilateral contracts  if the offeror expressly reserves the power to revoke the offer until the offerees performance is complete then the offer is illusory and cannot give rise to a unilateral contract but noting exceptions holding that the offerors signature on the offerees conditional acceptance bound the offeror to all the terms therein holding that an offer to donate cannot be an offer to sell holding that a written offer accepted by parol may constitute a sufficient memorandum of the contract provided the person making the offer is the party to be charged