Hi there, Can you share me some idea about this question. Thanks.

Felipe borrowed $100 from Gustavo in 1998, when the Phil P - US$ exchange rate was P56 - US$1. On March 1, 2008, Felipe tendered to Gustavo a cashier's check in the amount of P4,135 in payment of his US$ 100 debt, based on the Phil P - US$ exchange rat at that time. Gustavo accepted the check, but forgot to deposit it until Sept. 12, 2008. His bank refused to accepted the check because it had become stale. Gustavo now wants Felipe to pay him in cash the amount of P5,600. Claiming that the previous payment was not in legal tender, and that there has been extraordinary deflation since 1998, and therefore, Felipe should pay him the value of the debt at the time it was incurred. Felipe refused to pay him again, claiming that Gustavo is estopped from raising the issue of legal tender, having accepted the check in March, and that it was Gustavo's negligence in not depositing the check immediately that caused the check to become stale. Can Felipe validly refuse to pay Gustavo again?