For a sinusoidal electromagnetic wave in the vacuum, such that as explained by the equations Ey(x,t) = Emax cos(kx-wt) and Bz(x,t)= Bmax cos(kx-wt), determine the average energy density in the electric field in terms of the average energy density in the magnetic field (uM). Describe your answer in terms of the variable (uM) and suitable constants.