The Letter Grades Earned by Students in a Speech Class

The letter grades earned by students in a speech class included (with 'A' being the best grade possible and 'F' being the worst grade possible) : A, B, C, D, and F. Letter grade of 'A' had a relative frequency of 15%, grade of 'B' had a relative frequency of 20%, grade of 'C' had a relative frequency of 30%, letter grade of 'D' had a relative frequency of 20%, and letter grade of 'F' had a relative frequency of 15%. What is the cumulative relative frequency for a letter grade of 'C'?

A) 15%
B) 35%
C) 65%
D) 85%