Ignore friction in the following situations and rank the net changes of the gravitational potential energy (lowest first).
I. When a 0.15-kg apple falls from a tree branch to a level ground 2.0 m below, it bounces 3 times and then stops.
II. A person tosses a 0.60-kg ball at $30^o$ from a height of 1.0 m and the ball lands and comes to rest on a 0.50-m high leaf pile.
III. A girl leans from a window and tosses a set of 0.10-kg keys from a height of 4.0 m to a friend leaning from a window above and who catches the keys at the height of 7.0 m.