Car has a 1-liter gas mileage 12 km, another two 1-litre gas 14 km downhill by cars, each car must use at least oil as possible, how to ride the same way.
1 liter of petrol cars at a distance of 12 kilometers a second stick oil 1 liter each vehicle moving at 14 kilometers to oil, at least much. We are sailing on the same.