Question $5$

A bar with volume $500m^3$ has $50$ smokers in it$,$ each smoking two cigarettes per hour. An individual cigarette emits, among other things, about $1\mathrm{.}4mg$ of formaldehyde $($HCHO$).$ Formaldehyde converts to carbon dioxide with a reaction rate coefficient $k=\frac{0\mathrm{.}40}{h}r.$ Fresh air enters the bar at a rate of $1000\frac{m^3}{h}r,$ and stale air leaves at the same rate.

$($a$)$ Assuming complete mixing, estimate the steady$-$state concentration of formaldehyde in the air.

$($b$)$ How does the result compare with the threshold for eye irritation of about $0\mathrm{.}05ppm?$