In a math class, the distribution of grades was as follows: Grade A B C D F Number of students 6 13 9 4 2 If we select a student at random (Grade A-6 students)(Grade B-13 students)(Grade C-9 students) (Grade D-4 students)(Grade F-2 students)

(a) What is the probability that the student will have at least a C in the class?

(b) What is the probability that the student will have an A in the class, if it is known that the student has at least a C?