4. A 180 kg sumo wrestler on roller skates, rolling at 5 m/s to the left, collides elastically with
another sumo wrestler of mass 215 kg who is rolling at 3.5 m/s to the right on his roller skates. If
the speed of the 180 kg wrestler after the collision is 2 m/s in his original direction, what is the
speed of the second wrestler?