Решение задачи N4667 теория вероятностей

4667. There are products of four grades n1=4, n2=2, n3=3, n4=2. M items are taken at random to control. Determine the probability that among them m1=2 is first-class, m2=1, m3=2 and m4=1 are second, third and fourth grades, respectively.

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