The Effective Atomic Number $(EAN)$ of iron in potassium ferricyanide 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 $M(CO)_5$
$ii$. $MO_3F$

In $K_4[Fe(CN)_6]$,the $E.A.N.$ of $Fe$ is

Which of the following follows the $EAN$ rule?

The Effective Atomic Number $(EAN)$ of $Co$ in $[Co(NH_3)_6]^{3+}$ is:

What is the value of the effective atomic number $(EAN)$ of cobalt in the $[Co(NH_3)_6]^{3+}$ complex,given that the atomic number of $Co$ is $Z=27$?