[问答题]
(a) A box sits at rest on rti ;p:4h ogu6a ( +5vp 27,djda75j wdwthexls rough 30$^{\circ}$ inclined plane. Draw the free-body diagram, showing all the forces acting on the box.
(b) How would the diagram change if the box were sliding down the plane?
(c) How would it change if the box were sliding up the plane after an initial shove?