A bicycle rider covers his onwards journey from A to B at 10 km/hr and during the return journey from B to A, he covers the same distance at 8 km/hr. If he finishes the onward and return journey in 4 $$\frac{1}{2}$$ hours then the total distance covered by him during the entire journeyis

A

30km

B

40km

C

50km

D

20km