A box with a mass of 10 kg and a muzzle velocity of 1 m/s slides down a rough plane, inclined 30 from the horizontal. The box stops after traveling 1 m along the plane. For this route, find:

(a) the change in the kinetic energy of the box;

(b) the change in the potential energy of the box;

(c) the work of the frictional force.