A $208-$L drum $0\mathrm{.}4m$ in diameter containing PCE is open in a small drum storage area $5m$

$5m2\mathrm{.}5m$ high. The temperature is $25C.$ and the atmospheric pressure is $1$atm.

Ventilation in the structure provides four changes of air per hour. Determine the

following:

a$.$ The volatilization rate of PCE from the drum

b$.$ The steady$-$state PCE concentration $($ppm$)$ in the structure. Assume $k=0\mathrm{.}2.$