A block of mass M is pulled along a horizontal frictionless surface by a rope of mass m,as shown in Fig. 5-63. A horizontal force acts on one end of the rope. (a) Show that the rope must sag, even if only by an imperceptible amount.Then, assuming that the sag is negligible, find (b) the acceleration of rope and block, (c) the force on the block from the rope,and (d) the tension in the rope at its midpoint.