A 4-kg box is placed on a slope that makes an angle of 0 - 30" above the horizontal. The coefficient of static friction between the box and the slope surface is s = 0.6, and the corresponding coefficient of kinetic friction is Uk = 0.2. If the box slides down the slope by 3 m, what can be said about the work done by each of the forces acting on the box? For convenience, a free-body diagram containing these forces is included in the figure. N 4 kg 30 - O Wgravity > Wnormal > Wfriction O Wfriction > Wgravity > Wnormal O Wfriction > Wnormal > Wgravity O Wgravity > Wfriction > Wnormal O' Wnormal > Wfriction > Wgravity