A motorcycle stunt rider jumped across the snake river. the path of his motorcycle was given approximately by the function: H(t)= -0.0005x^2 +2.39x+600, where H is measured in feet above the river and x is the horizontal distance from his launch ramp. How high above the river was the launch ramp? what was the riders maximum height above the river, and how far was the rider from the ramp when he reached the maximum height?