Solution of problem N3791 probability theory total prob

3791. The box contains 8 parts belonging to workshop No. 1, 4 parts — workshop No. 2, and 6 parts — workshop No. 3. The probability that a part will be defective for workshop No. 1 is 0.2, for workshop No. 2 - 0 , 1, and shop number 3 produces 12% of the marriage. At random, the Quality Control Department selects the part to be checked, find the probability that it will be standard.