the bar in example had vlume

$5$

$0$

$0$

m

$3$

with fresh air entering at the rate of

$1$

$0$

$0$

$0$

m

$3$

$/$

hr

$.$

$$suppose when the bar opens at

$5$

pm

$,$

$$the air is clean. if formaldehide, with decay rate kd

$=$

$0$

$.$

$4$

$0$

$/$

hr

$,$

$$is emitted from cigarette smoke at the constant rate of

$1$

$4$

$0$

mg

$/$

hr starting at

$5$

pm

$,$

$$what would the concentration be at

$6$

pm