A class in advanced physics is comprised of 10 juniors, 30seniors, and 10 graduate students. The final grades show that 3 ofthe juniors, 10 of the seniors, and 5 of the graduate studentsreceived an A for the course. If a student is chosen at random fromthis class and is found to have earned an A, what is theprobability that he or she is a senior?
Does P(B|A) = provided P(A) > 0 apply here? If so, what isP(A∩B)? Is P(A) the total population; i.e. 50 students?