What is the effective atomic number of cobalt in $[Co(NH_3)_6]^{3+}$ if $Co$ has atomic number $Z=27$?

$EAN$ of $Fe$ in $[Fe(C_2O_4)_3]^{3-}$

What is the Effective Atomic Number $(EAN)$ of $Cu$ in $[Cu(NH_3)_4]^{2+}$?

$a$. 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 $M(CO)_5$
$ii$. $MO_3F$

In the brown ring complex,if $NO$ is considered as a neutral ligand,then the $EAN$ would:

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