Intensity and energy density, help?

Question

What is the average total energy density in electromagnetic radiation that has an intensity of 495 W/m2 (in J/m3)?

Answer 1

I am taking the number  495 W/m2 = the average intensity for a plane wave =

S = E^2(max)/[2(mu)(c)]

This makes use of the fact that the average of the square of a sinusoidal function over a whole number of periods is just 1/2.

Also note:

B(max) = E(max)/c

Electric energy density = (1/2)(epsilon)(Emax)^2

Magnetic energy density = (1/2)(mu)Bmax)^2