A local company is concerned about the number of days missed by its employees due to illness. A random sample of 10 employees is selected. The number of days absent in one year is listed below. An incentive program is offered in an attempt to decrease the number of days absent. The number of days absent in one year after the incentive program is listed below.

Employee	A	B	C	D	E	F	G	H	I	J
Days Absent Before the Incentive	3	13	11	1	14	8	8	9	4	1
Days Absent After the Incentive	1	2	2	0	2	9	9	1	6	9

Find the mean difference d