Suppose a driver wants to drive from the top of a mountain to the bottom. The road is 50 km long and the top of the mountain is 2500 m higher than the bottom. If the driver travels slowly at 60 km/hr, how much energy will their battery gain or lose during the trip? (Hint: Since the change in kinetic energy of the vehicle is zero, the sum of the work done on the car from all sources - gravity, rolling friction, air resistance, and the motor - must also be zero. If the motor does negative work, then is is acting as a generator and charging the battery; if the motor does positive work, then it will drain the battery.)