Three guests to a tea party sit down in three chairs. Then the host re-arranges them according

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Question:

Three guests to a tea party sit down in three chairs. Then the host re-arranges them according to a pre-made seating chart (a) What is the probability that all of the guests may stay in their chairs? (b) What is the probability that at least one guest may stay in her chair? Hint: Just write down all the sample points. Don't try to use counting rules.