a 500 kg crate is on a rough surface inclined at 30°. A constant external force P = 4000 N is applied horizontally to the crate. The force pushes the crate a distance of 3.0 m up the incline, in a time interval of 9.2 s, and the velocity changes from ν1 = 1.0 m/s to ν2 = 2.8 m/s. The work done by the friction force is closest to: I have no idea how to start this. I tried just using the regular work equation or conservation of energy and did not find the answer.