A forecasting method has produced the following over the past five months. What is the mean squared error?

Actual

Forecast

Error

$|$Error$|$

$10$

$8$

$2$

$2$

$8$

$11$

$3$

$3$

$10$

$8$

$2$

$2$

$6$

$6$

$0$

$0$

$9$

$7$

$2$

$2$

$3\mathrm{.}42$

None of the above

$5\mathrm{.}20$

$4\mathrm{.}20$

$2\mathrm{.}92$