A ball A of mass 2m is at the top of a frictionless shute at height 5h above the ground and another ball B of mass m is at rest on the horizontal surface at the end of the shute at height h above the ground. Ball A starts to slide from rest down the shute and hits ball B which is projected, after the impact, off the end of the shute. If the coefficient of restitution between the balls is 0.5, how far does ball B go horizontally before it hits the ground?