Based on the steady-state box model, list TWO things that

Based on the steady-state box model, list TWO things that can be done to the situation in the previous question about the smokers to reduce the steady-state concentration of the smoke and what each thing does with respect to the parameters of the steady-state box model formula.
An example would be: make some smokers leave the room–reduces the source rate of smoke
[Try to state these as briefly as possible. It is not necessary to give a detailed explanation of each, but there should be something that specifically states what is done. Note that there may be many more than two things that can be done; just pick two that involve two distinct changes that we can make. For example, you cannot have two things that modify only the source rate of smoke.]