Consider the following results from the last ten periods of student enrollment forecast by the Operations Management department chairman.

Period

Forecast

Actual

$1$

$25$

$26$

$2$

$32$

$31$

$3$

$42$

$45$

$4$

$53$

$50$

$5$

$64$

$70$

$6$

$70$

$72$

$7$

$81$

$78$

$8$

$88$

$90$

$9$

$95$

$93$

$10$

$102$

$105$

Determine the MAD for period $5$ for the department chairman's forecast.