Solving problem N3892 Bayesian probability theory

3892. Three workers handle the same type of parts. The first one processed 30 parts for a shift, the second - 25, the third - 15. The probability of marriage for the first worker is 0.04, for the second - 0.02, for the third - 0.03. From the total output per shift, one detail was taken and tested at random. a) Find the probability that it will be defective. b) A piece taken at random was defective. Find the probability that it is processed by the second worker.