A man carries a 50 kg backpack up a flight of stairs. Each step is 10.0 cm high and the man climbs 150 steps. He then walks 100m on a horizontal surface. (a) How much work did the man do on the backpack while climbing the steps? (b) How much work did the man do on the backpack while walking on the horizontal surface? (c) The man then drops the backpack from a balcony. It falls to the level of the bottom of the stairs. What is the speed of the backpack when it reaches its original level (solve using energy methods, not kinematics; neglect friction)