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Of the emails you receive 20% are spam on average

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Of the emails you receive 20% are spam on average. Your spam filter is able to detect 90% of them but also misclassifies as spam 15% of the genuine emails.

(a) If an email arrives and is marked spam, what is the probability that it really is spam?

(b) If an email arrives and is not marked spam, what is the probability that it is legitimate?