A class grading system is structured as follows:

A ~ No more than 6% of students
A- and above ~ No more than 12% of students
B+ and above ~ No more than 21% of students
B and above ~ No more than 30% of students
B- and above ~ No more than 40% of students
C+ and above ~ No more than 50% of students

If the average grade for a midterm is 72.1%, and the standard deviation of that midterm 12.5%, what grade would a score of 77.5% earn?

Thank you very much in advance.