The table below gives the annual sales (in millions) of a product.
| year | 1998 | 1999 | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006 |
|---|---|---|---|---|---|---|---|---|---|
| sales | 236 | 254 | 268 | 278 | 284 | 286 | 284 | 278 | 268 |
What was the average rate of change of annual sales
(a) Between 2000 and 2001
millions of dollars/year
(b) Between 2000 and 2004
millions of dollars/year