Xylene $($C$8$H$10)$ is an organic solvent and a constituent of gasoline. Elevated exposure can cause damage to the nervous and respiratory systems. The United States Occupational Safety and Health Administration has established an occupational exposure limit of $435$ mg$/$m$3.$ Given pressure and temperature of P $=1$ atm and T $=293$ K$,$ what is the mole fraction of xylene that corresponds to $435$ mg$/$m$3?$