A bike rider covers a fixed distance at a speed of 60 km/h and returns back at a speed of 80 km/h. What is his average speed?

A

$$71\frac{1}{7}$$ km/h

B

$$68\frac{4}{7}$$ km/h

C

$$53\frac{3}{7}$$ km/h

D

$$63\frac{1}{7}$$ km/h