If a ball is thrown upwards at 20 ft/sec, the height h after t seconds is given by h = -16t^2 + 20t. How many seconds does it take for the ball to

If a ball is thrown upwards at 20 ft/sec, the height h after t seconds is given by h = -16t^2 + 20t. How many seconds does it take for the ball to reach its maximum height, and what is this height?