The titration graph below plots the $pH$ change with addition of $0\mathrm{.}10$MNaOH$(aq)$ to $100mL$ of solution initially composed of equimolar $C{H}_{3}C{O}_{2}H(aq)$ and $NaC{H}_{3}C{O}_2(aq),$ at $25\mathrm{.}0C$ : $(20)$

The identity of the titrant is $q,$

The identity of the analyte is $C{H}_{3}C{O}_2{H}_{3}C{H}_{3}C{O}_2^{-}$

The $p{K}_a$ of the acid in the equimolar miTure estimated from the graph is