Given that ${\mathrm{E}}^{\mathrm{o}}$ values of ${\mathrm{Ag}}^{+}/\mathrm{Ag},{\mathrm{K}}^{+}/\mathrm{K},{\mathrm{Mg}}^{2+}/\mathrm{Mg}$ and ${\mathrm{Cr}}^{3+}/\mathrm{Cr}$ are 0.80 V, -2.93 V, -2.37 V and -0.74 V respectively. Therefore the order for the reducing power of the metal is