Multiply the first two by 0.5, indicating that both experts have passed; Who said that one passed and the other failed, and then passed the audit? The two experts in the preliminary examination may pass or fail, so they should be multiplied by 2, and 0.3 represents the approval of the review.

The probability of all four papers failing is 0.6 4 = 0. 1.296. Only one of the four papers passing is 4 times 0.6 3 times 0.4=0.3456.

So the probability that at least two papers pass is1-0.1296-0.3456 = 0.5248.

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