The table gives the cumulative sales of ipods since their introduction. Cumulative iPod Sales Sales Year (million ipods) 2003 2.52 2004 4.936 2005 27.933 2006 68.642 2007 121.072 2008 175.2 (a) Find the function for the quadratic model that gives sales in million ipods, where x is the number of years after 2003, with data from 0 s x $ 5. (Round all numerical values to three decimal places.) s ( x) = million ipods (b) Write the derivative for the sales model. (Round all numerical values to three decimal places.) s'(x) = million ipods per year (c) Calculate the rate of change of cumulative sales in 2006. (Round your answer to three decimal places.) million ipods per year Interpret the rate of change of cumulative sales in 2006. (Round your answer to three decimal places.) In 2006, cumulative iPod sales were ---Select--- v by million per year