A 380 kg piano slides 2.9 m down a 25◦ incline and is kept from accelerating by a man who is pushing back on it parallel to the incline (figure below). Determine:
(a) the force exerted by the man,
(b) the work done on the piano by the man,
(c) the work done on the piano by the force of gravity, and
(d) the net work done on the piano. Ignore friction.