No one could figure out how to do this extra credit question on our final.

A bowl of toluene is placed on a pan balance. A bubbler is suspended in the toluene and 25 liters per minute of air is passed through the toluene. Over one minute, 2.44 grams of toluene is lost due to evaporation. Air flow in the hood is 172 cubic feet per minute and the volume of the enclosure is 14.2 cubic feet. The temperature is 75 degrees F and pressure is 1019 mb. molecular weight of toluene is 92.1.

I started converting the standard measurements to metric (temp is 24 Celsius; 14.2 cubic feet is 402 L; pressure becomes 1.009 atmospheres). Should I calculate the concentration for 1 minute, then take airflow into account... kinda like a snapshot?

Thanks!