A rider is riding his bike along the sides of a square ground. He drives the bike with the speed of 10 km/h along one side, 15 km/h along another side, 18 km/h along the third side, and 20 km/h along the last side and reaches the starting point. What is the average speed of the bike along the sides of the ground?
1
14.7 km/h
2
13.9 km/h
3
15.6 km/h
4
16.3 km/h
5
11.2 km/h