5 sold a car for P500,000 to B. Unknown to b, the car then had ked engine block, the replacement of which would cost 00. Despite his knowledge of this defect, S obtained a waiver B of the latter's right under the warranty against hidden ts. Subsequently, the car was wrecked due to the recklessness who only then discovered the defects. What kind of waiver was to S by B? Is S liable? If yes, for how much