4115. There are 1,400 lamps, 650 belong to the first batch, 350 to the second batch, 400 to the third batch. In the first batch of 9%, in the second - 2%, in the third - 3% 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)