#### Answer

average rate of change in $[2009, 2013] =1,320.5$ thousands per year
The number new of motor vehicles sold in the United States increased at an average of $1,320.5$ thousands per year from 2009 to 2013.

#### Work Step by Step

RECALL:
The average rate of change of a function in the interval $[a,b]$ is given by the formula:
average rate of change$=\dfrac{f(b)-f(a)}{b-a}$
The given graph shows that:
$f(2009)=10,602$
$f(2013)=15,884$
Use the formula to obtain:
average rate of change in $[2009, 2013]$
= $\dfrac{15884-10602}{2013-2009}
\\=\dfrac{5282}{4}$
$\\=1,320.5$ thousands
Thus, the number new of motor vehicles sold in the United States increased at an average of $1,320.5$ thousands per year from 2009 to 2013.