A car travels for 40 minutes at a speed of 40 km/h, for another 50 minutes at a speed of 45 km/h and for next 90 minutes at a speed of 60 km/h. What is the average speed (in km/h) of the car for the entire journey?
1
\(49\frac{1}{4}\)
2
\(50\frac{1}{2}\)
3
\(51\frac{7}{18}\)
4
\(50\frac{5}{8}\)