If the volume of a sphere of radius 'r' i equal to the volume of a cylinder whose base radius is $$\frac{r}{2}$$ and heighth, then h =

A

$$\frac{4}{3}r$$

B

$$\frac{8}{3}r$$

C

$$\frac{16}{3}r$$

D

$$\frac{20}{3}r$$