please prove it using UT=VT(phi*) where phi* is the replicating strategy.

Consider an American Contingent Claim Y in the T-period CRR model. Suppose the buyer does not exercise the ACC at time T1. For this scenario, show that UT1=1+r1Ep[UTFT1] where Ut denotes the minimum amount of wealth that the seller of the ACC must have at time t in order to ensure that the seller has enough to cover the payoff if the buyer cashes in the claim in time {t,t+1,,T}