A 384 kg piano slides 3.6 m down a(n) 27° incline and is kept from accelerating by a man who is pushing back on it parallel to the incline (see figure). The effective coefficient of kinetic friction is 0.40. (a) Calculate the force exerted by the man. (b) Calculate the work done by the man on the piano. (c) Calculate the work done by the friction force. (d) Calculate the work done by the force of gravity.