AP Macroeconomics students were given an exam on a particular topic. Each week, they were tested with a comparable exam on the same topic and the average score for the class was measured. The function M (t) = 80 – 20log(t + 1) models the average score for the class after t weeks. How many weeks will it take for the average score of the class to equal 60? 8 weeks

9 weeks (the answer)

10 weeks

11 weeks