$(A)$ In octahedral complex: $\left[ M \left( H _{2} O \right)_{6}\right]^{2+}$
$C.F.S.E.$ $=\left(-0.4 \Delta_{0}\right) \times 4+\left(+0.6 \Delta_{0}\right) \times 2+0 \times P$
$(B)$ In tetrahedral complex: $\left[ M \left( H _{2} O \right)_{4}\right]^{2+}$
$C.F.S.E.$ $=\left(-0.6 \Delta_{t}\right) \times 3+\left(+0.4 \Delta_{t}\right) \times 3+0 \times P$
$=-0.6 \Delta_{ t }$
$(i)\, [CoCl_3 (NH_3)_3]$ $(ii)\, [Co(en)_3]Cl_3$
$(iii)\, [Co(C_2O_4)_2(NH_3)_2]^-$ $(iv)\, [CrCl_2(NH_3)_2(en)]^+$