3962. The store received electric lamps produced by two plants. Among them, 80% are manufactured by the first plant, and the rest - by the second. It is known that 10% of the lamps of the 1st plant and 20% of the lamps of the 2nd plant contain a hidden defect. The probability of purchasing a lamp without a defect in this store is equal to

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