Решение задачи N4687 теория вероятностей

4687. There are products of four grades n1=2, n2=3 n3=1, n4=3. M items are taken at random to control. Determine the probability that among them m1=2 is first-class, m2=1, m3=0 and m4=2 are second, third and fourth grades, respectively.

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