4104. Of the 1000 lamps, 810 belong to the 1st installment, 70 to the second, and the rest to the third. In the first batch of 10%, in the second 1%, in the third 2% of defective lamps. One lamp is selected at random. Determine the probability that the selected lamp is defective.

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