A 50.0 kg student uses an improvised 75 kg raft to cross a heavily flooded street. He noticed that as he jumps to the sidewalk opposite the street with a speed of 1.5 m/s relative to the flood, the raft moves away. With what speed will the raft move relative to the flood? Assume that the raft is stationary before the student jumps to the sidewalk. Neglect fluid friction.​