Answer
$0.75$ percentage points in unemployment per percentage point increase of GDP
Work Step by Step
The average rate of change of $f(x)$ over the interval $[a, b]$ is $\displaystyle \frac{f(b)-f(a)}{b-a}$
Units: "(unit of f(x) ) per (unit of x)"
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Given the interval $[0.4]$ and the graph,
a=$0,\ \quad $(0,5) on the graph $\Rightarrow f(0)=5$
b=$4,\ \quad $(4,8) on the graph $\Rightarrow f(4)=8$
$\displaystyle \frac{f(b)-f(a)}{b-a} =\displaystyle \frac{8-5}{4-0}$
$=\displaystyle \frac{3}{4}$ (percentage points in unemployment) per (percentage point increase of GDP)
$= 0.75$ percentage points in unemployment per percentage point increase of GDP
