A galvanic cell which makes use of the following reaction at 298K. $Cr_2O_7^{2-}+14H^++6Fe^{2+}\rightarrow 2Cr^{3+}+6Fe^{3+}+7H_2O$.Given : $E^{\large\circ}(Cr_2O_7^{2-},H^+,Cr^{3+}|Pt)=1.33V;E^{\large\circ}(Fe^{3+},Fe^{2+}|Pt)=0.77V$.Reducing $[Cr^{3+}]$ to 0.50M,keeping all other concentrations at unity,the emf of the cell would be changed by

Question

$\begin{array}{1 1}5.92mV\\2.96mV\\-5.92mV\\-2.96mV\end{array}$