Answer
($C$)
Work Step by Step
The average rate of change of $f$ over the interval $[a, b]$ is
Average rate of change of $f\displaystyle \ \ =\frac{f(b)-f(a)}{b-a}$
The units of the average rate of change of $f$ are units of $f(x)$ per unit of $x$.
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We see that the line connecting the points $4$ and $10$ is roughly parallel to the regression line (equal slopes). Thus, the answer is (C).
