A 100W power source emits green light at a wavelength $\lambda=5000\overset{\circ}{A}$. How many photons per minute are emitted by the source?

Question

$\begin{array}{1 1}(a)\;1.5\times 10^{22}&(b)\;2\times 10^{21}\\(c)\;3\times 10^{24}&(d)\;2.5\times 10^{21}\end{array}$