The function $h$, defined by $h(t)=-5t^2+10t+7.5$, models the height of a diver above the water (in meters) $t$ seconds after the diver leaves the board. For each question, explain your reasoning.

1. How high above the water is the diving board?
2. When does the diver hit the water?
3. At what point during her descent toward the water is the diver at the same height as the diving board?
4. When does the diver reach the maximum height of the dive?
5. What is the maximum height the diver reaches during the dive?