A square wooden raft floats on a lake. The density of the water in the lake is 1000 kg/m². The sides of the raft are 2.0m long and the thickness of the raft is 0.20 m. The mass of the raft is 700 kg. How many barrels, each of mass 100 kg, could be placed on the raft before its surface sinks to the surface of the water?​