The effective atomic number $(EAN)$ of iron in the complex $[(\eta^5 - C_5H_5) Fe(CO)_2Cl]$ is

What is the $EAN$ of $Co$ in $[Co(NH_3)_6]^{3+}$?

What is the oxidation state of cobalt in a coordination complex if its $EAN$ is $36$ and the value of $C.N.$ is $6$? (Given: Atomic number of cobalt = $27$).

Among $V(CO)_6$,$Cr(CO)_5$,$Cu(CO)_3$,$Mn(CO)_5$,$Fe(CO)_5$,$[Co(CO)_3]^{3-}$,$[Cr(CO)_4]^{4-}$,and $Ir(CO)_3$,the total number of species isoelectronic with $Ni(CO)_4$ is. . . . . [Given atomic number : $V=23$,$Cr=24$,$Mn=25$,$Fe=26$,$Co=27$,$Ni=28$,$Cu=29$,$Ir=77$ ]

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 $Z=27$?

Which of the following complex compounds/ions obeys the Sidgwick $EAN$ rule?