3903. The collector received 3 boxes of parts: in the first box 40 parts, 20 of them painted; in the second - 50, of which 10 are painted; in the third - 30 parts, 12 of them painted. Find the probability that at random the extracted part from the randomly taken box will be colored.

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