The following curve for the conductometric titration is obtained when -

What is the $\mathrm{emf}$ at $25 °\mathrm{C}$  for the cell, $\mathrm{Ag},\begin{array}{c}\mathrm{AgBr}\text{ (s) }{\mathrm{Br}}^{-}\\ \mathrm{a}=0.34\end{array}\left|\begin{array}{ll}{\mathrm{Fe}}^{3+}& {\mathrm{Fe}}^{2+}\\ \mathrm{a}=0.1& \mathrm{a}=0.02\end{array}\right|\mathrm{Pt}$ .

The standard reduction potentials for the half-reactions $\mathrm{AgBr}+{\mathrm{e}}^{-}\to \mathrm{Ag}+{\mathrm{Br}}^{-}$ and ${\mathrm{Fe}}^{3+}+{\mathrm{e}}^{-}\to {\mathrm{Fe}}^{2+}$ are $+0.0713 \mathrm{V}$ and $+0.770 \mathrm{V}$ respectively.

Two weak acid solutions $\mathrm{HA}$ and ${\mathrm{HA}}_2$ each with the same concentration and having $\mathrm{pKa}$ values $3$ and $5$ are placed in contact with hydrogen electrode ($1 \mathrm{atm}$,$25 °\mathrm{C}$) and are interconnected through a salt bridge. The $\mathrm{emf}$ of the cell is: