How is the average energy density in an electromagnetic wave related to the magnetic field?

An electromagnetic wave is travelling in $x$-direction with electric field vector given by $\vec{E}_{y} = E_{0} \sin(kx - \omega t) \hat{j}$. The correct expression for the magnetic field vector is:

The ratio of the magnitude of the magnetic field $(B_0)$ and electric field intensity $(E_0)$ of a plane electromagnetic wave in free space with permeability $\mu_0$ and permittivity $\varepsilon_0$ is (Given that $c$ is the velocity of light in free space):

$A$ plane electromagnetic wave propagating in $x$-direction is described by $E_{y} = (200 \ Vm^{-1}) \sin [1.5 \times 10^7 t - 0.05 \ x]$. The intensity of the wave is: (Use $\epsilon_0 = 8.85 \times 10^{-12} \ C^2 \ N^{-1} \ m^{-2}$) (in $Wm^{-2}$)

The velocity of electromagnetic waves is parallel to which of the following?

What is the amplitude of the electric field in a parallel beam of light of intensity $\left(\frac{15}{\pi}\right) \text{ W/m}^2$ (in $\text{ N/C}$)? $\left[\text{Assume} \frac{1}{4 \pi \varepsilon_0} = 9 \times 10^9 \text{ Nm}^2/\text{C}^2\right]$