The following graph shows the percentage y of all music sold that was rap music x years af...

The following graph shows the percentage y of all music sold that was rap music x years after 1992. The y-intercept of 8.6 indicates that 8.6% of all music sold in 1992 was rap music.

Source: World Almanac and Book of Facts 1998.

a. Determine the intervals of x- values for which the function is increasing

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b. Determine the interval of x-values for which the function is decreasing

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c. Determine the interval of x-value for which the average rate of change of the function is increasing

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d. Determine the interval of x-value for which the average rate of change of the function is decreasing