An amusement park ride goes over the top of a circular hill of radius 18m. The total mass of the cart is 1200kg. a) If the speed at the top of the hill is 11m/s what is the magnitude and direction of the normal force from the track on the car? b) If the speed is 14m/s at the top of the hill, what is the magnitude and direction of the normal force from the track on the cart? c) what is the maximum speed the cart could go without flying off the track?