An electric car travelled a total distance of 120 km. During the first 60 km, it travelled at an average speed of 60 km/hr. During the last 60 km, it travelled at an average speed of 120 km/hr. What was its average speed over the total distance of 120 km?
1) 72 km/hr
2) 80 km/hr
3) 90 km/hr
4) 108 km/hr
