10 point physics questionnn?

Question

A cargo barge is loaded in a saltwater harbor for a trip up a freshwater river. If the rectangular barge is 3.0 mx 20.0 m and 6.80 m deep water floating in the saltwater harbor(density=1025 kg/m^3), 

how deep will it sit in the river, which is 

freshwater (density=1000 kg/m^3)? 

volume of displaced water-

 Weight of the barge-

Answer 1

Archimedes points out that a floating body will displace its own WEIGHT of fluid. so 3*20 * 6.8 * 1025 = 3 * 20 * h * 1000  ( this seems a very strange SHAPE for a barge. Highly unstable. )