The weight of a body in air is 100N. How much will it weight in water, if it displaced 400 cc of water?

U=Vρwg ⇒  U=(400×10−6)(1000)(9.8) ⇒  U=3.92 N  W'=W−U ⇒  W'=100−3.92 ⇒  W'=96.08 N