Four successive members of the first row transition elements are listed below with atomic numbers. Which one of them is expected to have the highest ${\mathrm{E}}_{{\mathrm{M}}^{3+}/{\mathrm{M}}^{+2}}^0$ value

$\begin{array}{l}{E}_{C{r}^{3+}/C{r}^{2+}}^0=-0.41\mathrm{V};E_{M{n}^{3+}/M{n}^{2+}}^0=+1.57\mathrm{V};\\ E_{F{e}^{3+}/F{e}^{2+}}^0=+0.77\mathrm{V};E_{C{o}^{3+}/C{o}^{2+}}^0=+1.97\mathrm{V}\text{ SRP value }\end{array}$

normally increases from left to right in the period of d block elements. Some SRP value are exceptionally higher due to stability of product ion. For e.g. 

$E_{{\mathrm{Mn}}^{3+}/{\mathrm{Mn}}^{2+}}^0=+1.57\mathrm{V};E_{{\mathrm{Co}}^{3+}/{\mathrm{Co}}^{2+}}^0=+1.97\mathrm{V}.$