A $1\mathrm{.}50L$ sample of water found in the environment is tested for lead. The sample is combined with

$1\mathrm{.}00L$ of a $1\mathrm{.}00mol{L}^{-1}$ potassium iodide solution. This results in a lead$($II$)$ iodide precipitate. After

the precipitate has completely dried, it has a mass of $157mg.$ Since the iodide was very much in

excess, we can assume all the lead ions have precipitated. What is the concentration of lead in the

water sample $($in $mol{L}^{-1})?$