A roller-coaster car of mass 1.70 x 10" kg is initially at the top of a rise at point @. It then moves 39.4 m at an angle of 45.0 below the horizontal to a lower point , (a) Find both the potential energy of the system when the car is at points ( and @ and the change in potential energy as the car moves from point @ to point , assuming y = 0 at point & potential energy at @ 464147.72 potential energy at change in potential energy -464147.72 (b) Repeat part (a), this time choosing y = 0 at point @, which is another 15.0 m down the same slope from point . potential energy at@ 453614.4 X Your response differs from the correct answer by more than 10%. Double check your calculations. J 249900 potential energy at B X Your response differs from the correct answer by more than 10%. Double check your calculations. J change in potential energy -464147.72