A roller coaster car with a mass of 1900 kg starts at rest from a point 73 m above the ground. At point B, it is 17 m above the ground. (a) What is the initial potential energy of the car? (b) What is the potential energy at point B? If the initial kinetic energy was zero and the work done against friction between the starting point and point B is 2,000 J, (c) what is the kinetic energy of the car at point B? Use g = 9.8 m/s²