18. A punter kicks a football straight up in the air from a 50. m tall cliff. When the ball leaves the punter's foot it is traveling 15 m/s. What is the highest point the football reaches relative to the ground? What is the speed of the ball when it returns to the height of the punter's foot? What is the velocity of the ball just before it hits the ground? What is the total amount of time the ball was in the air? How much time did it take for the ball to reach its highest point?