4. In the picture below, a 1000 kg car starts at point A and travels down a hill through points B. C, and D. 5 m 5 m 7 m (a) Using the vertical level of point D as the reference level, calculate: i. the car's gravitational potential energy at points A, B. C, and D PE (point A) = PE ( point B) = PE ( point C) = PE (point D) = ii. the car's change in gravitational potential energy (APE) in traveling from point A to B. A to C, and A to D. APE (A to B) = APE (A to C) = APE (A to D) = (b) Using the vertical level of point A as the reference level, calculate: i. the car's gravitational potential energy at points A, B. C, and D PE (point A) = PE (point B) = PE (point C) = PE (point D) = ii. the car's change in gravitational potential energy (APE) in traveling from point A to B. A to C, and A to D. APE (A to B) = APE (A to C) = APE (A to D) =