A machine produces photo detectors in pairs. Tests show that the first photo detector is acceptable with probability 3/5. When the first photo detector is acceptable, the second photo detector is acceptable with probability 4/5. If the first photo detector is defective, the second photo detector is acceptable with probability 2/5. Use the tree diagram to answer the following questions:
• What is the probability that exactly one photo detector of a pair is acceptable?
• What is the probability that both photo detectors in a pair are defective?