Given :

$\mathrm{C}{\mathrm{o}}^{3+}+{\mathrm{e}}^{-}\to \mathrm{C}{\mathrm{o}}^{2+};{\mathrm{E}}^{\circ }=+1.81\mathrm{V}$

$\mathrm{P}{\mathrm{b}}^{4+}+2{\mathrm{e}}^{-}\to \mathrm{P}{\mathrm{b}}^{2+};{\mathrm{E}}^{\circ }=+1.67\mathrm{V}$

$\mathrm{C}{\mathrm{e}}^{4+}+{\mathrm{e}}^{-}\to \mathrm{C}{\mathrm{e}}^{3+};{\mathrm{E}}^{\circ }=+1.61\mathrm{V}$

$\mathrm{B}{\mathrm{i}}^{3+}+3{\mathrm{e}}^{-}\to \mathrm{Bi};{\mathrm{E}}^{\circ }=+0.20\mathrm{V}$

Oxidizing power of the species will increase in the order :