In a sample of 1000 U.S. adults, 180 dine out at a restaurant more than once per week. Two U.S. adults are selected at random without replacement.
(a) Find the probability that both adults dine out more than once per week.
(b) Find the probability that neither adult dines out more than once per week.
(c) Find the probability that at least one of the two adults dines out more than once per week.
(d) Which of the events can be considered unusual? Explain.