Engineers want to construct a straight and level road \(600 \mathrm{ft}\) long
and \(75 \mathrm{ft}\) wide by making a vertical cut through an intervening hill
(see the accompanying figure). Heights of the hill above the centerline of the
proposed road, as obtained at various points from a contour map of the region,
are shown in the accompanying figure. To estimate the construction costs, the
engineers need to know the volume of earth that must be removed. Approximate
this volume, rounded to the nearest cubic foot. [Hint: First set up an
integral for the cross-sectional area of the cut along the centerline of the
road, then assume that the height of the hill does not vary between the
centerline and edges of the road.]
$$
\begin{array}{cc}
\hline \begin{array}{l}
\text { HORIZONTAL } \\
\text { DISTANCE } x \text { (ft) }
\end{array} & \begin{array}{c}
\text { HEIGHT } \\
h(\mathrm{ft})
\end{array} \\
\hline 0 & 0 \\
100 & 7 \\
200 & 16 \\
300 & 24 \\
400 & 25 \\
500 & 16 \\
600 & 0
\end{array}
$$