The sun radiates electromagnetic energy at the rate of $3.9 \times 10^{26} \mathrm{~W}$. Its radius is $696 \times 10^{8} \mathrm{~m}$. The intensity of sunlight (in $\mathrm{Wm}^{-2}$ ) at the solar surface will be
(a) $4.3 \times 10^{6}$
(b) $4.5 \times 10^{7}$
(c) $5.6 \times 10^{7}$
(d) $5.8 \times 10^{6}$