Instantaneous Rate of Change

Can someone help me solve this problem... I need to calculate the instantaneous rate of change for the following points:

- 1985
- 1995
- 2000
- 2006

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Based on this data:

Year Public Sector Employment (Number of People in Millions)

1981 2.69009

1982 2.72483

1983 2.74130

1984 2.76072

1985 2.79665

1986 2.84086

1987 2.87816

1988 2.94450

1989 2.96726

1990 3.02734

1991 3.05678

1992 3.06323

1993 3.03748

1994 3.00269

1995 2.95784

1996 2.85133

1997 2.78940

1998 2.77897

1999 2.76987

2000 2.78673

2001 2.81360

2002 2.84346

2003 2.90811

2004 2.94086

2005 2.97973

2006 3.04614

The equation I got for this was y = 0.0002x^3 - 1.3853x^2 + 2763.2x - 2000000

Can you please just help me with the first one... After i understand how to do the first oen I'll know how to do the rest.

Thanks :)