Two blocks placed one above the other are connected through a cable AB as shown in the figure. The coefficient of static friction between all the surfaces is 0.4 and the kinetic friction is 0.3. The system is initially at rest. Find: (a) the minimum force P to start the motion. (b) the minimum force required to maintain constant speed once the motion starts. (c) the minimum force to start the motion if the cable is disconnected right at the beginning.