4 g mixture of NaOH, Na_2 CO_3 and some inert impurities was first titrated with N/10 HCl using phenolphthalein as an indicator, 17.5 mL of HCl was…

$\displaystyle 4$ g mixture of NaOH, $\displaystyle \mathrm{Na}_2 \mathrm{CO}_3$ and some inert impurities was first titrated with $\displaystyle \frac{\mathrm{N}}{10} \mathrm{HCl}$ using phenolphthalein as an indicator, $\displaystyle 17.5$ mL of HCl was required at the end point. After this methyl orange was added and titrated. $\displaystyle 1.5$ mL of same HCl was required for the next end point. The weight percentage of $\displaystyle \mathrm{Na}_2 \mathrm{CO}_3$ in the mixture is \_\_\_\_. (Rounded-off to the nearest integer)