Решение задачи N4672 теория вероятностей

4672. There are products of four grades n1=1, n2=2, n3=3, n4=5. M items are taken at random to control. Determine the probability that among them m1=1 is first-class, m2=1, m3=2 and m4=3 are second, third and fourth grades, respectively.

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