The electric field component of a time harmonic plane EM wave traveling in a non-magnetic lossless dielectric medium has amplitude of 2V/m. If the relative permittivity of the medium is 4, the magnitude of the time-average power density vector $$(in W/m^2)$$ is

A

$$\frac {1}{30 \pi}$$

B

$$\frac {1}{120 \pi}$$

C

$$\frac {1}{60 \pi}$$

D

$$\frac {1}{240 \pi}$$