A stone is thrown up from the ground, the trajectory of the stone can be described as h(t) = −6t^2 + 18t, where t is the time in seconds after the throw and h is a height (in feet) of the stone above the ground.
(a). When does the stone reach its maximum height? What is the maximum height that the stone would
reach?
(b). How long will it take to hit the ground?