A ball is thrown vertically upward from the top of a building 1600 feet tall with an initial velocity of 80 ft per second. The distance d(t), in feet, of the ball from the ground after t seconds is d(t)=1600+80t-16t^2 . After how many seconds is the ball at its maximum height? Find the maximum height of the ball. How long will it take the ball to hit the ground?