Trace organic compounds in the atmosphere are first concentrated and then measured by gas chromatography. In the concentration step, several liters of air are pumped through a tube containing a porous substance that traps organic compounds. The tube is then connected to a gas chromatograph and heated to release the trapped compounds. The organic compounds are separated in the column and the amounts are measured. In an analysis for benzene and toluene in air, a 3.00- L sample of air at 748 torr and 23^oC was passed through the trap. The gas chromatography analysis showed that this air sample contained 89.6 ng of benzene (C₆H₆) and 153 ng of toluene (C₇H₈). Calculate the mixing ratio and number of molecules per cubic centimeter for both benzene and toluene.