One way the U$.$S$.$ Environmental Protection Agency $($EPA$)$ tests for chloride contaminants in water is by titrating a sample of silver nitrate solution. Any

chloride anions in solution will combine with the silver cations to produce bright white silver chloride precipitate.

Suppose an EPA chemist tests a $200.$ mL sample of groundwater known to be contaminated with iron$($III$)$ chloride, which would react with silver nitrate

solution like this:

$FeC{l}_3(aq)+3AgN{O}_3(aq)3$AgCl$(s)+Fe(N{O}_3{)}_3(aq)$

The chemist adds $49\mathrm{.}0mM$ silver nitrate solution to the sample until silver chloride stops forming. He then washes, dries, and weighs the precipitate. He

finds he has collected $5\mathrm{.}2mg$ of silver chloride.

Calculate the concentration of iron$($III$)$ chloride contaminant in the original groundwater sample. Round your answer to $2$ significant digits.