A ball is launched vertically upward from the roof of a building that is 13 feet above the ground. For t≥0, the ball's vertical displacement h(t), in feet, from the rooftop is modeled by h(t)=−4(t−3)2+36. A positive displacement indicates that the ball is above the rooftop, and a negative displacement indicates that the ball is below the rooftop.
Which choice is the time, in seconds after launch, at which the ball hits the ground?