$9)$ A forecasting method has produced the following over the past five months. What is the mean absolute deviation? $\_\_\_\_\_\_$

Actual

Forecast

Error

$|$Error$|$

$10$

$11$

$-1$

$1$

$8$

$10$

$-2$

$2$

$10$

$8$

$2$

$2$

$6$

$6$

$0$

$0$

$9$

$8$

$1$

$1$

A$)0\mathrm{.}8$ B$)1\mathrm{.}2$ C$)0\mathrm{.}0$ D$)-1\mathrm{.}1$ E$)5\mathrm{.}6$