A pilot who is flying at an altitude of 10 000 feet is forced to eject from his airplane. The path that his ejection seat takes is modeled by the equation h(t) = -16t^2 + 90t + 10000 where h(t) is his altitude in feet and t is the time since his ejection in seconds. Estimate at what time, t, the pilot is at a maximum altitude. Explain how the maximum altitude is related to the slope of the tangent line at certain points.