The table gives the cumulative sales of iPods since their introduction.

Cumulative iPod Sales

$s(x)=9\mathrm{.}341x^2-5\mathrm{.}225x+1\mathrm{.}22$ million iPods

$($b$)$ Write the derivative for the sales model. $($Round all numerical values to three decimal places.$)$

$s^{\text{'}}(x)=$

million iPods per year

$($c$)$ Calculate the rate of change of cumulative sales in $2004.($Round your answer to three decimal places.$)$

$$ million iPods per year

Interpret the rate of change of cumulative sales in $2004.($Round your answer to three decimal places.$)$

In $2004,$ cumulative iPod sales were $---$ Select$---$ by million per year.