3608. Among those entering the assembly, parts turned out to be defective: 1% from the first machine, 2% from the second, 2.5% from the third, and 5% from the fourth. Machine productivity is 4: 3: 2: 1 respectively. Taken as a luck item was standard. Find the probability that it is made on the first machine.

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