Suppose an unrelated 77-year-old man, 76-year-old woman, and 82-year-old woman ...

Suppose an unrelated 77-year-old man, 76-year-old woman, and 82-year-old woman are selected from a community.
(a) What is the probability that all three of these individuals have Alzheimer's disease?
(b) What is the probability that at least one of the three people has Alzheimer's disease?
(c) Suppose we know one of the three people has Alzheimer's disease, but we don't know which one. What is the conditional probability that the affected person is a woman?