Given the following balanced chemical equation of a reaction system at equilibrium: $3$H$\_(2($g$))+$N$\_(2($g$))2$NH$\_(3($g$))$

An amount of $12\mathrm{.}00$ moles of hydrogen and $4\mathrm{.}00$ moles of nitrogen are initially added to a $4\mathrm{.}00$L flask. What are the equilibrium concentrations of H$\_(2($g$))$ and N$\_(2($g$))$ if $6\mathrm{.}00$ moles of NH$\_(3($g$))$ are found in the flask at equilibrium?