13-50. Block A has a mass mA and is attached to a spring having a stiffness k and unstretched length lo. If another block B, having a mass me, is pressed against A so that the spring deforms a distance d, show that for separation to occur it is necessary that d> 2k8(mA + mB)/k, where is the coefficient of kinetic friction between the blocks and the ground. Also, what is the distance the blocks slide on the surface before they separate?