Final answer:
If events A and B are mutually exclusive, the probability of them both happening is 0. The probability of either event A or event B occurring is the sum of their individual probabilities.
Step-by-step explanation:
If events A and B are mutually exclusive, it means they cannot occur at the same time. Therefore, the probability of both events happening simultaneously, denoted as P(A AND B), is equal to 0. In this case, the probability of either event A or event B occurring, denoted as P(A OR B), is simply the sum of the individual probabilities of each event: P(A OR B) = P(A) + P(B).