Suppose a particular email user has a 20% chance that a received email is spam. Assume each email is independent of each other as to whether it is spam or not. Note that the total number of regular emails when the first spam email is received is a geometric probability.

a) (3) What is the probability that this user will receive her first spam email on the third email?

b) (3) What is the probability that this user will receive her first spam email on or before the third email?

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