What is the $EAN$ of $Fe$ in $[Fe(CN)_6]^{3-}$?

The effective atomic number of Iron $(Z = 26)$ in $[Fe(CN)_6]^{3-}$ is

$a$. Answer the following questions:
$i$. Which element of the first transition series has the highest second ionisation enthalpy?
$ii$. Which element of the first transition series has the highest third ionisation enthalpy?
$iii$. Which element of the first transition series has the lowest enthalpy of atomisation?
$b$. Identify the metal and justify your answer:
$i$. Carbonyl $M(CO)_5$
$ii$. $MO_3F$

The $EAN$ of $Fe$ in $K_4[Fe(CN)_6]$ is

The $EAN$ of $Ni$ in $[Ni(CO)_4]$ is ....

The $EAN$ of cobalt is $36$ in $[Co(NH_3)_2O_2(en)Cl]$. Thus,$O_2$ is