Q11 ans b but I think answer should be a
If in the first two tests the machines are found to be non faulty
We will certainly know that the rest of the two machines are faulty
If this case is also counted then answer should be a not b
there are two cases.
FF OR CC
so for FF
2/4 * 1/3
same for CC 2/4 *1/3
So the ans sud be 1/3
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