On a forward somersault dive, Nina's height, h, in metres, above the water is approximately modelled by the function h(t) = -5t^2+ 7t + 4,
where t is the time, in seconds, after she leaves the diving board. Graph
the function and use the graph to complete the following. a) Find Nina's
maximum height above the water. b) How long does it take her to reach
the maximum height? c) How long is it before she enters the water? d)
How high is the board above the water?