Solution of problem N3952 probability theory total prob

Solution of problem N3952 probability theory total prob

3952. Electric bulbs are manufactured at three plants. The first plant produces 40% of the total number of light bulbs, the second 50%, the third 10%. The production of the first plant contains 75% of standard lamps, the second 85%, the third 90%. What is the probability that the lamp purchased in the store will be standard?

Additional information:

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