The scores for students taking a particular exam are summarized in the following frequency distribution. Score Number of Students 91 - 100 5 81 - 90 5 71 - 80 9 61 - 70 6 51 - 60 4 41 - 50 2 Use this frequency distribution to approximate the mean score for students taking the exam. Treat the data as population data. Round your answer to two decimal places