Q$4$ The stream shown below receives wastewater effluent from two point sources at Sites $1$ and $2.$ There are $2$ dischargers and $3$ check points. The concentration of pollutant at the sites $2$ and $3$ should not exceed the maximum desired concentration. The values of the parameters are given in Table Q$4$: Determine the level of wastewater treatment $($waste removed$)$ at sites $1$ and $2$ to achieve the desired concentrations at sites $2$ and $3$ at a minimum total cost

Where;

$W_1,W_2=$ Pollutant loads day