$E^{\circ}=\frac{2.303 \mathrm{RT}}{n F} \log K_{\mathrm{eq}} \quad$ i.e., $K_{\mathrm{eq}}<1$
${[Fe\,{(CN)_6}]^{4 - }}\, \to \,{[Fe{(CN)_6}]^{3 - }}\, + \,{e^ - }\,;\,$ ${E^o}\, = \, - \,0.35\,V$
$\,F{e^{2 + }}\, \to \,F{e^{3 + }}\, + \,{e^ - }\,;$ ${E^o}\, = \, - \,0.77\,V$
$Zn|ZnS{O_4}_{(0.01{\kern 1pt} M)}||CuS{O_4}_{(1.0{\kern 1pt} M)}|Cu$