.
4.1
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If A and B are mutually exclusive events, then
P(A or B) = P(A) + P(B).
If A and B are independent events, then
P(A or B) = P(A) + P(B) - P(A)*P(B).
4.2
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The formulation is DEFECTIVE.
Check it with your source; then fix and re-edit; then re-post to the forum.
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The rule of this forum is
ONE and ONLY ONE problem per post.
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Instead of packing many problems in one post inaccurately, you better submit one problem per post accurately (!)