A man drives from station A to station B 60 km away at an average speed of 30 kph and return to A at an average speed of 20 kph. What was the average speed of the man in the whole journey?

A man drives from station A to station B 60 km away at an average speed of 30 kph and return to A at an average speed of 20 kph. What was the average speed of the man in the whole journey?