1. On an examination, the average grade was 86 and the standard deviation was 7. If 17% of the class is given A's and the grades are curved to follow...

In a mathematics examination the average grade was 83 and the standard deviation was 5. All students with grades from 87 to 90 received a grade of B. if the grades are approximately normally distributed and 15 students received a B grade, how many students took the examination?