Bala travels first one-third of the total distance at the speed of 10 km/h and the next one-third distance at the speed of 20 km/h and the last one – third distance at the speed of 60 km/h. What is the average speed of Bala?
1
18 km/h
2
19 km/h
3
16 km/h
4
12 km/h