This problem asks for an average yearly rate of change over a time interval. Since x represents years since 2005, the year 2013 corresponds to x=8, and the year 2015 corresponds to x=10. Use the average rate of change formula:

10−8

f(10)−f(8)

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Evaluating the model gives f(8)=240(1.12)

8

≈594.23 and f(10)=240(1.12)

10

≈745.40. The total change is approximately 151.17 dollars over 2 years. Dividing by 2 gives about 75.59 dollars per year. Since the question asks for the average yearly rate, not the total increase, the correct answer is B.