In a roller coaster, a car has x joules of potential energy when it is resting at the top of the hill. the car moves downhill and reaches the bottom of the hill, where it moves quickly. assuming no friction, what does the law of conservation of energy predict about the car?

a)at the bottom, the car has x joules of potential energy.
b)at the bottom, the car has x joules of mechanical energy.
c)at the bottom, the car has more than x joules of kinetic energy.
d)at the bottom, the car has more than x joules of mechanical energy.