Three cities, A, B, and C are located such that they form the vertices of an equilateral triangle if joined by straight lines. Rashid travels from A to B at the speed of 40 km/h, from B to C at the speed of 60 km/h and from C to A at the speed of 72 k /h. Find the average speed of Rashid for the entire journey.

A

54 km/h

B

$$56\frac{2}{3}$$

C

55 km/h

D

$$57\frac{1}{3}$$