Given below are the half-cell reactions :
${Mn}^{2+}+2 e^{-} \longrightarrow {Mn} ; E^{\circ}=-1.18 {~V}$
$2\left({Mn}^{3+}+e^{-} \longrightarrow {Mn}^{2+}\right) ; E^{\circ}=+1.51 {~V}$
The $E^{\circ}$ for $3 {Mn}^{2+} \longrightarrow {Mn}+2 {Mn}^{3+}$ will be
(a) $-0.33 {~V}$; the reaction will occur
(b) $-2.69 \mathrm{~V}$; the reaction will not occur
(c) $-2.69 \mathrm{~V}$; the reaction will occur
(d) $-0.33 \mathrm{~V}$; the reaction will not occur.