Physics Work,Power & Energy Level: Misc Level

A 50 kg crate slides down a 5.0 m loading ramp that is inclined at an angle of 25% to the horizontal.A worker pushes on the crate parallel to the surface of the ramp so that the crate slides down with a constant velocity. If the coefficient of kinetic friction between the crate and the ramp is 0.33, how much work is done by each of the following?(a)the worker,(b)the force of friction, (c) the force of gravity, (d) what is the net work done on the crate?