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**Mush** a) Will occur when either the accident is CORRECTLY attributed to faulty brakes, OR when the accident is INCORRECTLY attributed to faulty brakes. If an event occurs when either one event OR another event happens, then you simply add their probabilities. Hence 0.04+0.03.

b) This will occur when two things happen simultaneously. The accident happened due to faulty brakes, AND the accident was attributed to faulty brakes. When we want the probabilities of two things happening simultaneously, we multiply their probabilities. Hence (0.04)(0.03).