A 800 kg roller-coaster car is initially at the top of a rise, at point A. It then moves 135 ft, at an angle of 40.0° below the horizontal, to a lower point B. (a) Choose the car at point B to be the zero configuration 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 coaster moves. GPE = mgy cos theta This is my attempt to solve, however I keep getting that my answer is wrong. (800kg)(9.8)(41.15m)x cos 40 =247,138.19J Can someone please let me know what is incorrect in my process?