The diagram shows object A moving along a sloping surface and passing point q. At the moment when A passes point q, object B is released from rest at point p and moves with constant acceleration to meet A at point r. Points p, q, and r lie on the same straight line, and the distance between points p and r is d. At point r, the velocity of B is 4/3 times that of A. Assuming that the mass of each object is negligible and that all friction is absent, what is the distance between A and B at the instant when A reaches its highest point?

Vi -O B A B a A