Suppose that, at the end of last semester, Marie gave her introductory statistics class a final exam. After grading these exams, she created a histogram illustrating the distribution of exam scores for the 68 students in the class. A histogram of exam scores shows 2 scores between 20 and 30 points, 1 between 40 and 50 points, 10 between 50 and 60 points, 11 between 60 and 70 points, 17 between 70 and 80 points, 18 between 80 and 90 points, and 9 between 90 and 100 points. Each of the bars in this histogram includes only the left endpoint of the interval, except for the bar representing scores between 90 and 100 points, which also includes the right endpoint. What percentage of students scored between 50 and 70 points on the exam