Sun gives light at rate of $\;1400 Wm^{-2}\;$ of area perpendicular to direction of light . Assume $\;\lambda\;$ (sun light )= $\;6000 A^{0}\;.$ Then no.of Photons emitted from sun/sec assuming average radius of earth's orbit is $\;1.49\times10^{11} m\;$ is

Question

$(a)\;2\times10^{36}\qquad(b)\;1.17\times10^{45}\qquad(c)\;1.96\times10^{72}\qquad(d)\;1.23\times10^{31}$