The reduction potential \( (E^\circ, \ \text{in V}) \) of \( \mathrm{MnO_4^- (aq)} / \mathrm{Mn(s)} \) is _______.
\([ \text{Given: } E^\circ_{(\mathrm{MnO_4^-(aq)}/\mathrm{MnO_2(s)})} = 1.68 \ \mathrm{V} ; \ E^\circ_{(\mathrm{MnO_2(s)}/\mathrm{Mn^{2+}(aq)})} = 1.21 \ \mathrm{V} ; \ E^\circ_{(\mathrm{Mn^{2+}(aq)}/\mathrm{Mn(s)})} = -1.03 \ \mathrm{V} ]\)
