What is the oxidation state of $Fe$ in $Fe(CO)_5$?

Write the formulas for the following coordination compounds:
$(a)$ Tetraammineaquachloridocobalt $(III)$ chloride
$(b)$ Potassium tetrahydroxidozincate $(II)$
$(c)$ Potassium trioxalatoaluminate $(III)$
$(d)$ Dichloridobis(ethane$-1,2-$diamine)cobalt $(III)$
$(e)$ Tetracarbonylnickel $(0)$

The $IUPAC$ name of $[Pt(NH_3)_4][PtCl_4]$ is:

The brown ring complex compound is $[Fe(H_2O)_5(NO)]SO_4$. What is the oxidation state of iron in this complex?

Oxidation number of $Cr$ in $[Cr(CO)_6]$ is

In the complex $K_2Fe[Fe(CN)_6]$,which of the following statements is correct?