To maintain a speed of \( 80 \, \text{km/h} \) by a bus of mass \( 500 \, \text{kg} \) on a plane rough road for \( 4 \, \text{km} \) distance, the work done by the engine of the bus will be _____ \( \text{KJ} \). (The coefficient of friction between tyre of bus and road is \( 0.04 \).)
