A Rubex tablet, weighing $1\mathrm{.}35$g$,$ was dissolved in $50$mls of water to which

$2$mls of $4$ mol$/$L $(4$M$)$ NaOH was added.

This solution was made up to the mark in a $200$ml volumetric flask with

water. It was found $10$mls of this $($filtered$)$ solution required an average

titre of $6\mathrm{.}50$ml of $0\mathrm{.}05$M HCl for neutralisation.

Show your clear step$-$by$-$step calculation,

in order to determine the percentage $($two decimal places$)$ of Vitamin C

$($Ascorbic acid$)$ in this tablet based on these experimental results.