Answer
${{\$}} 0.15$ per year
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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Using the formula above, we get:
$\displaystyle \frac{P(26)-P(1)}{26-1}=\frac{97.2-93.45}{25}=0.15$ (dollars per year)
