#### Answer

The sale of desktop computers per year decreased (on average) by-171.3 million/year from 2010 to 2013.

#### Work Step by Step

To calculate the average rate of change between two points $(x_1,y_1)$ and $(x_2,y_2)$, we use the formula:
$\displaystyle average~rate~of~change=\frac{y_2-y_1}{x_2-x_1}$
Here, we use the points $(2010,\ 7390)$ and $(2013,\ 6876)$:
$\displaystyle average~rate~of~change=\displaystyle \frac{6876-7390}{2013-2010}=\frac{-514}{3}=-171.3$ million/year
Thus the sale of desktop computers per year decreased (on average) by-171.3 million/year from 2010 to 2013.