4686. There are products of four grades n1=3, n2=2 n3=3, n4=1. M items are taken at random to control. Determine the probability that among them m1=2 is first-class, m2=2, m3=2 and m4=0 of the second, 3rd and fourth grade, respectively.

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