A differential pulley (chain hoist) is shown in Fig. 7-6. Two toothed pulleys of radii r = 10 cm and R = 11 cm are fastened together and turn on the same axle. A continuous chain passes over the smaller (10 cm) pulley, then around the movable pulley at the bottom, and finally around the 11 cm pulley. The operator exerts a downward force F on the chain to lift the load Fw. (a) Determine the IMA. (b) What is the efficiency of the machine if an applied force of 50 N is required to lift a load of 700 N?