Hi, I have the follwoing physics question to ask, Plesae help with hints.

Question

"Two people are standing on a 2.5-m-long platform, one at each end. The platform floats parallel to the ground on a cushion of air, like a hovercraft. One person throws a 5.9-kg ball to the other, who catches it. The ball travels nearly horizontally. Excluding the ball, the total mass of the platform and people is 111 kg. Because of the throw, this 111-kg mass recoils. How far does it move before coming to rest again?"

Thx