Which one follow 18 electron octet rule?

The 18 electron rule is used for predicting the stability and rationalizing the formula, especially organomettalic complexes. The number of valence electrons of the given species are as follows: $\left[\mathrm{Mn}(\mathrm{CO})_5\right]-\mathrm{Mn}\left\{[\mathrm{Ar}]_{18} 3 \mathrm{~d}^5 4 \mathrm{~S}^2\right\}=7 \text{ valence }$ electrons $\left[\mathrm{Cr}(\mathrm{CO})_5\right]-\operatorname{Cr}\left\{[\mathrm{Ar}]_{18} 3 \mathrm{~d}^4 4 \mathrm{~S}^2\right\}=6 \text{ valence }$ electrons $\left[\mathrm{Fe}(\mathrm{CO})_5\right]-\mathrm{Fe}\left\{[\mathrm{Ar}]_{18} 3 \mathrm{~d}^6 4 \mathrm{~S}^2\right\}=8 \text{ valence }$ electrons $\therefore\left[\mathrm{Fe}(\mathrm{CO})_5\right]$ follow 18 electron octet rule.