Boxes are transported from one location to another in a warehouse by means of a conveyor belt that moves with a constant speed of 0.81 m/s. At a certain location the conveyor belt moves for 4.6 m up an incline that makes an angle of 11° with the horizontal, then for 4.6 m horizontally, and finally for 4.6 m down an incline that makes an angle of 11° with the horizontal. Assume that a 1.0 kg box rides on the belt without slipping. At what rate is the force of the conveyor belt doing work on the box (a) as the box moves up the 11° incline, (b) as the box moves horizontally, and (c) as the box moves down the 11° incline?