\subsection{Exercise for Homework 4}\label{M4_P3_HW4}
\begin{enumerate}
\item At a different time the concentration function, for concentrations at diffetent depths in a settlement tank is $c(h) =\dfrac{120}{\sqrt[3]{2.05}-\sqrt[3]{h}}$.
\begin{enumerate}
\item Estimate the mass of chemical in the tank by assuming that the concentration is constant for `sheets' of depth 0.25cm.
\item Find the best estimate that Mathematica will allow, for the mass of chemical in the tank.
\end{enumerate}
\item Another tank measures 10m by 4m and is 1.5m deep. The concentration function is found to be $c(h)=\dfrac{100}{\sqrt{1.6}-\sqrt{h}}$
\begin{enumerate}
\item State a differential model for $A(h)$, the mass of chemical in the top $h$ metres of the tank.
\item Find the increase in the mass of chemical from the top to the bottom of the tank.
\end{enumerate}
\end{enumerate}
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