Akhil rides first 12 km at a speed of 16 km/h and further 6 km at a speed of 20 km/h. Find his average speed (in km/h).

A

$$18\frac{1}{5}$$

B

$$16\frac{4}{5}$$

C

$$17\frac{1}{2}$$

D

$$17\frac{1}{7}$$