In sodium nitroprusside the oxidation number, coordination number and $\mathrm{EAN}$ of iron, respectively are: 

Which of the following obeys the $\mathrm{EAN}$ rule?

(a) $\left[\mathrm{Fe} {\mathrm{\eta }}^5-{\left({\mathrm{C}}_5{\mathrm{H}}_5\right)}_2\right] \mathrm{with} {\mathrm{Fe}}^{2+}$.

(b) $\left[\mathrm{Co}\left(\mathrm{NO}\right){\left(\mathrm{CO}\right)}_3\right] \mathrm{with} \mathrm{Co}°$.

(c) $\left[{\mathrm{Mn}}_2{\left(\mathrm{CO}\right)}_{10}\right] \mathrm{with} \mathrm{Mn}°$.

(d) $\left[\mathrm{V} {\left(\mathrm{CO}\right)}_6\right] \mathrm{with} {\mathrm{V}}^{1-}$.