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 tracking signal for period 4 for the department chairman's forecast.

0.6

-0.6

0.0

-1.9