The electric field measured in the far field of an antenna at a distance of 50m is 1 $$\frac{V}{m}$$. The average powerdensity at a distance of 500m from the antenna is

A

$$26.6 \mu$$ W/m$$^2$$

B

$$0.1 \mu$$ W/m$$^2$$

C

$$10 \mu$$ W/m$$^2$$

D

$$13.3 \mu$$ W/m$$^2$$