An hourly temperature on February 15, 2015 showed the following:

Time *** Temperature
Noon *** - $\displaystyle {11}$
1:00pm *** - $\displaystyle {9}$
2:00pm *** - $\displaystyle {5}$
3:00pm *** - $\displaystyle {4}$
4:00pm *** + $\displaystyle {2}$
5:00pm *** + $\displaystyle {3}$
6:00pm *** - $\displaystyle {5}$
7:00pm *** - $\displaystyle {9}$
8:00pm *** - $\displaystyle {11}$
9:00pm *** - $\displaystyle {17}$




The change in temperature from 2:00pm to 8:00pm =