(Solved): 2.74 A class in advanced physics is composed of 10 juniors, 30 seniors, and 10 graduate students. T ...

2.74 A class in advanced physics is composed of 10 juniors, 30 seniors, and 10 graduate students. The final grades show that 3 of the juniors, 10 of the seniors, and 5 of the graduate students received an \( A \) for the course. If a student is chosen at random from this class and is found to have earned an \( A \), what is the probability that he or she is a senior?