3921. Among 350 mechanisms 160 first, 110 - second, 80 - third grade. The probability of marriage among the mechanisms of the first grade is 0.01, among the second grade is 0.02, among the third grade is 0.04. One mechanism is taken. Determine the probability that the mechanism is serviceable.

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