A car having cross sectional area of its front equal to A is travelling on a highway at a speed v. The viscous drag force acting on the car is known to be given as `F_(v)=CArhov^(2)` .Where `rho` is density of air and C is a constant which depends on the shape of the car. The petrol used by the car produces E joules of energy per kg of it burnt. Calculate the mileage (in km/kg) of the car if the combined efficiency of its engine and transmission is f.