A car driver travels from plane to hill station which are 200 km apart at an average speed of 40 km/h. In the return trip, he covers the same distance at an average speed of 20 km/h. Then, the average speed of the car over the entire distance of 400 km is
1
25 km/h
2
30 km/h
3
24.33 km/h
4
26.67 km/h