A box weighing 77.0N rests on a table. A rope tied to the box runs vertically upward over a pulley and a weight is hung from the other end (Fig.4-40). Determine the force that the table exerts on the box if the weight hanging on the other side of the pulley weighs
(a) 30.0 N
(b) 60.0 N and
(c) 90.0 N.