For purposes of making on-campus housing assignments, a college classifies its students as
Priority A (seniors), Priority B (juniors), and Priority C (freshmen and sophomores). Of the
students who choose to live on campus, 10% are seniors, 20% are juniors, and the rest are underclassmen. The most desirable dorm is the newly constructed Gold dorm, and 60% of the seniors elect to live there. 15% of the juniors also live there, along with only 5% of the freshmen and sophomores.

a) Draw a tree diagram to explain all the different outcomes.

b) What is the probability that a randomly selected resident of the Gold dorm is not a senior?

c) What is the probability that a randomly selected resident who does not select a Gold dorm is a junior?