A $1000-$kg roller coaster car is initially at the top of a hill, at point A$.$ It then moves $89$ m$,$ at an angle of $40$ degrees below the horizontal, to a lower point B$.$

Choose the height at point B to be the zero potential point for gravitational potential energy of the roller coaster$$ Earth system. Find the potential energy of the system when the car is at points A and B$,$ and the change in potential energy as the car moves between these points.

$$

Repeat part a$,$ setting the zero potential point at the height of point A$.$