The figure below shows an arrangement of pulleys designed to facilitate the lifting of a heavy load L. Assume that friction can be ignored everywhere and that the pulleys
 to which the load is attached weigh a total of 20.0 lb. An 840-lb load is to be raised 12.0 ft.
(a) What is the minimum applied force F that can lift the load?
(b) How much work must be done against gravity in lifting the 840-lb load 12.0 ft?
(c) Through what distance must the applied force be exerted to lift the load 12.0 ft?
(d) How much work must be done by the applied force F to accomplish this task?