Calculate the mean deviation and its coefficient from the following data, relating to height (to the nearest cm) of $100$ children.

Heights(cm)	$60$	$61$	$62$	$63$	$64$	$65$	$66$	$67$	$68$
No. of children	$2$	$0$	$15$	$29$	$25$	$12$	$10$	$4$	$3$