A man covers half part of a certain distance at 45 km/hr. He covers 40 percent of remaining distance at the speed of 8 km/hr and covers rest of the distance at the speed of 24 km/hr. What is his average speed for the entire journey?

A

164/7 km/hr

B

144/7 km/hr

C

156/7 km/hr

D

128/7 km/hr