Boxes are transported from one location to another in a warehouse by means of a conveyor belt that moves with a constant speed of $0.50 \mathrm{~m} / \mathrm{s}$. At a certain location the conveyor belt moves for $2.0 \mathrm{~m}$ up an incline that makes an angle of $10^{\circ}$ with the horizontal, then for $2.0 \mathrm{~m}$ horizontally, and finally for $2.0 \mathrm{~m}$ down an incline that makes an angle of $10^{\circ}$ with the horizontal. Assume that a $2.0 \mathrm{~kg}$ box rides on the belt without slipping. At what rate is the force of the conveyor belt doing work on the box as the box moves (a) up the $10^{\circ}$ incline, (b) horizontally, and (c) down the $10^{\circ}$ incline?