A man walks from P to Q at a speed 10 km/h, but comes back from Q to P at 12 km/h.
Find his average speed.

A

$$10\frac{10}{11}$$ km/h

B

$$11\frac{10}{11}$$ km/h

C

$$9\frac{10}{11}$$ km/h

D

$$\frac{10}{11}$$ km/h