1. The problem statement, all variables and given/known data The air in a small room 12x8x8 ft (768 ft^3 is the volume) is 3% carbon monoxide. Starting at t=0, fresh air containing no carbon monoxide is blown into the root at rate of 100 ft^3/min. If the air in the room flows out at same rate (100 ft^3/min), when will air in room be 0.01%? 2. Relevant equations s'(t) = (rate entering)(concentration entering) - (rate exiting)(concentration exiting) concentration = amount/volume 3. The attempt at a solution I don't need you to solve the problem for me, but I am having trouble getting started and figuring out what the concentration is. s'(t) = (rate entering)(concentration entering) - (rate exiting)(concentration exiting) s'(t) = (100)(?) - (100)(?) concentration = amount/volume Since it said at time t=0, fresh air containing *NO* carbon monoxide..., will the concentration entering be 0? And for the concentration exiting, will it be s(t)/768? so the s'(t) is: 0 - 100s(t)/768 Is this correct? I am contemplating about the 3% carbon monoxide, could this be the concentration entering??