A lagoon with volume $1,100$ m$3$ has been receiving a steady flow of a non$-$conservative waste $($rate constant$=0\mathrm{.}26/$day$)$ at a rate of $80$ m$3/$day for a long enough time to assume that steady$-$state conditions apply. The waste entering the lagoon has a concentration of $18$ mg$/$L$.$

A$.$ What would be the concentration of pollutant in the effluent leaving the lagoon?

B$.$ If the input waste concentration suddenly increased to $110$ mg$/$L$,$ what would the concentration in the effluent be $4$ days later?