Two identical blocks each of mass M are connected by a light inextensible string and can move on the surface of a rough horizontal table. The blocks are being towed at constant speed in a straight line by a rope attached to one of them. The tension in the tow rope is T0. What is the tension in the connecting string? The tension in the tow rope is suddenly increased to 4T0. What is the instantaneous acceleration of the blocks and what is the instantaneous tension in the connecting string?