A room having dimensions \(10 \mathrm{ft} \times 15 \mathrm{ft} \times 8
\mathrm{ft}\) originally contains \(0.001 \%\) carbon monoxide \((\mathrm{CO})\).
Suppose that at time \(t=0\), fumes containing \(5^{\circ}\); CO begin entering
the room at a rate of \(0.12 \mathrm{ft}^{3} \mathrm{~min}\), and that the
wellcirculated mixture is eliminated from the room at the same rate.
|al Find a formula for the volume \(f(t)\) of \(\mathrm{CO}\) in the room at time
\(t\).
(b) The minimum level of CO considered to be hazardous to health is
\(0.015^{\circ}\). After approximately how many minutes will the room contain
this level of \(\mathrm{CO}\) ?