Cost Curve Dean \(^{69}\) made a statistical estimation of the cost-output
relationship for a hosiery mill. The data for the firm is given in the
following table.
$$
\begin{array}{|l|llllll|}
\hline x & 45 & 56 & 62 & 70 & 74 & 78 \\
\hline y & 14 & 17 & 19 & 20.5 & 21.5 & 22.5 \\
\hline
\end{array}
$$
Here \(x\) is production in hundreds of dozens, and \(y\) is the total cost is
thousands of dollars.
a. Determine both the best-fitting quadratic using least squares and the
square of the correlation coefficient. Graph.
b. Using the quadratic cost function found in part (a) and the approximate
derivative found on your computer or graphing calculator, graph the marginal
cost. What is happening to marginal cost as output increases? Explain what
this means.