3819. In the workshop on three machines manufactured the same type of parts. The probability of failure-free operation of the first machine is 0.3, the second - 0.4, the third - 0.3. The probability of manufacturing a defective part on the first machine is 0.2, on the second - 0.3, on the third - 0.1. Find the probability that the selected part will be standard at random.

Detailed solution. Decorated in Microsoft Word 2003 (Quest decided to use the formula editor)