A flight from Pittsburgh to Charlotte has a 90% on-time record. From Charlotte to Jacksonville, North Carolina, the flight is on time 80% of the time. The return flight from Jacksonville to Charlotte is on time 50% of the time and from Charlotte to Pittsburgh, 90% of the time. Consider a round trip from Pittsburgh to Jacksonville on these flights. Assume the flights are independent.

a. What is the probability that all 4 flights are on time?
b. What is the probability that at least 1 flight is not on time?
c. What is the probability that at least 1 flight is on time?

d. Which events are complementary?