An automobile's engine produces 30hp while being driven at 50mph on a level highway. In those circumstances, the engine's power is used to overcome air drag, rolling resistance between the tires and the road, and friction in the drivetrain. Estimate the vehicle's fuel economy rating in the units of miles per gallon. The engine has an efficiency of 10%-15% and the Gas has a Density of 680 kg/m^3. Can you please show it worked out if possible?