The table below gives the annual sales (in millions) of a product. year 1998 1999 2000 2001 2002 2003 2004 2005 2006 sales 222 276 318 348 366 372 366 348 318 What was the average rate of change of annual sales a) Between 2003 and 2004 millions of dollars/year b) Between 2003 and 2006 millions of dollars/year