Task: Question Answering
Input (English): passage: One example of an event that is both collectively exhaustive and mutually exclusive is tossing a coin. The outcome must be either heads or tails, or p (heads or tails) = 1, so the outcomes are collectively exhaustive. When heads occurs, tails can't occur, or p (heads and tails) = 0, so the outcomes are also mutually exclusive.
 question: if events a and b are mutually exclusive are they also collectively exhaustive?
Output (English): Yes