Answer
The events are mutually exclusive.
Work Step by Step
$P(A\cup B)=P(A)+P(B)-P(A\cap B)$
If $A$ and $B$ are mutually exclusive events:
$-P(A\cap B)=0$
Then:
$P(A\cup B)=P(A)+P(B)-0=P(A)+P(B)$
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