4106. There are 1,200 lamps, 300 belong to the first batch, 200 to the second batch, 700 to the third batch. In the first batch of 7%, in the second - 6%, in the third - 5% 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)