The table below gives the annual sales (in millions) of a product. year 1998 1999 2000 2001 2002 2003 2004 2005 2006 sales 282 318 346 366 378 382 378 366 346 What was the average rate of change of annual sales a) Between 1998 and 1999 millions of dollars/year b) Between 1998 and 2002 millions of dollars/year