Answer
$\mathrm{The\ cost\ of\ removing} \ 75\%\ \mathrm{of\ pollutant\ is} \ \$20,100$
Work Step by Step
$\begin{array}{l}
\mathrm{To\ find\ the\ cost\ of\ removing\ 75\%\ of\ pollutant\ from\ the\ environment,\ set\ } x\mathrm{\ equal\ to\ 75}\\
(\mathrm{recall\ that\ the\ units\ of} \ x\ \mathrm{is\ thousands\ of\ dollars}) \ \mathrm{then} \ \mathrm{apply\ the\ cost-benefit\ model\ }\\
\mathrm{as\ follows} :\\
\begin{array}{ c l }
y & =\dfrac{6.7( 75)}{100-75}\\
& \\
& =\dfrac{502.5}{25}\\
& \\
& =20.10
\end{array}\\
\\
\mathrm{The\ cost\ of\ removing} \ 75\%\ \mathrm{of\ pollutant\ is} \ \$20,100
\end{array}$.
