3847. 70% of the parts arriving at the assembly, made by 1 automatic machine, give 2% of the scrap, and 30% of the parts entering the assembly, made by 2 automatic machine, give 5% of the scrap. Randomly taken detail was defective. What is the probability that, for good luck, the taken part made is made by 1 automatic.

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