3780. The warehouse receives the products of three factories, the products of the first factory being 40%, the second - 20%, and the third 40%. It is known that the average percentage of non-standard products for the first factory is 0.4%, for the second - 0.3%, for the third - 0.2%. It was a non-standard products. Find the probability that the randomly selected product will be the production of the first factory.

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