What is the value of the speed of light in free space?

$A$ point source of electromagnetic radiation has an average power output of $800\,W$. The maximum value of the electric field at a distance of $3.5\,m$ from the source will be.....$V/m$.

The magnetic field in a plane electromagnetic wave is given by $B = 3.01 \times 10^{-7} \sin(6.28 \times 10^2 x + 2.2 \times 10^{10} t) \, T$,where $x$ is in $cm$ and $t$ is in seconds. The wavelength of the given wave is ....... $cm$.

Intensity of sunlight is observed as $0.092 \, W/m^2$ at a point in free space. What will be the peak value of the magnetic field at that point? (Given: $\epsilon_0 = 8.85 \times 10^{-12} \, C^2 N^{-1} m^{-2}$,$c = 3 \times 10^8 \, m/s$)

The electric and the magnetic field,associated with an electromagnetic wave propagating along the $+z$-axis,can be represented by

The electric field of a plane electromagnetic wave propagating through a non-magnetic medium is given by $E = 20 \cos (2 \times 10^{10} t - 200 x) \, V/m$. The dielectric constant of the medium is equal to: (Take $\mu_r = 1$)