An ecologist wished to know whether certain species of aquatic insects have their ecological range limited by temperature. He collected the data in Table $8,$ relating the average daily temperature at different portions of a creek with the elevation (above sea level) of that portion of the creek. (The authors express their thanks to Dr. J. David Allen, formerly of the Department of Zoology at the University of Maryland, for providing the data for this exercise.)
(a) Find the straight line that provides the best least-squares fit these data.
(b) Use the linear function to estimate the average daily temperature for this creek at altitude 3.2 kilometers.
$$\begin{array}{cc} \text {Table 8 Relationship between Elevation and} \\ \text {Temperature in a Creek} \\
\hline & \text { Average Temperature } \\
\text { Elevation (kilometers) } & \text { (degrees Celsius) } \\
\hline 2.7 & 11.2 \\
2.8 & 10 \\
3.0 & 8.5 \\
3.5 & 7.5 \\
\hline
\end{array}$$