A man can row at a speed of 15/2 km/hr in still water. He goes to a certain point upstream and back to the starting point in a river which flows at 3/2 km/hr, then the average speed of the man for the total journey is:
1
5.2 km/hr
2
7.2 km/hr
3
6.2 km/hr
4
8.2 km/hr