In the reaction of oxalate with permanganate in acidic medium, the number of electrons involved in producing one molecule of ${\mathrm{CO}}_2$ is:

$25 \mathrm{mL}$ of the given $\mathrm{HCl}$ solution requires $30 \mathrm{mL}$ of $0.1 \mathrm{M}$ sodium carbonate solution. What is the volume of this $\mathrm{HCl}$ solution required to titrate $30 \mathrm{mL}$ of $0.2 \mathrm{M}$ an aqueous $\mathrm{NaOH}$ solution?