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\noindent {\bf Problem statement} Four containers are each 10 cm
tall. Each of them has a volume of 30 ${\rm cm}^3$ and each is being
filled by a liquid at the rate of 5 ${\rm cm}^3$ per minute. Here is a
picture of the containers:

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\centerline{\epsfbox{w3X.eps}}
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\line {\hskip .97in (A) \hskip .81in (B)\hskip 1.05in (C) \hskip .95in
(D)\hfil}

\medskip

\noindent a) For each of the containers, graph the height, $h(t)$, of
the level of the liquid in the containers measured in centimeters as a
function of time, $t$, measured in minutes.

\medskip

\noindent b) Which of the functions graphed in a) are continuous?
Explain your answers.

\medskip

\noindent c) Which of the functions graphed in a) are differentiable?
Explain your answers.

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