If X has a Poisson distribution such that $P(X=1)=P(X=2)$ then $P(X=3)$ is :

$\frac{4}{3}e^{-2}$ $\frac{1}{3}e^{-3}$ $\frac{2}{3}e^{-2}$ $\frac{5}{3}e^{-4}$

$\frac{4}{3}e^{-2}$