A $0\mathrm{.}68$ g sample of sterling silver was dissolved in concentrated nitric acid and this solution was diluted to $50$ mL with water. Subsequently, $29\mathrm{.}16$ mL of $0\mathrm{.}1$ M solution of hydrogen sulphide was required to precipitate all the silver ions, via the following reaction:

$2$Ag$++$S$2->$Ag$2$S

What is the mass percentage of silver in the sterling silver sample?