Misprints. Each page of a book contains N symbols, possibly mis- prints. The book contains n = 500 pages and r = 50 misprints. Show that32. Let

a, b,

c, d be four non-negative integers such that a+b+c+d= 13.

Find the probability p

(a,

b, c,

d) that in a bridge game the players North, East, South, West have

a, b,

c, d spades, respectively. Formulate a scheme of placing red and black balls into cells that contains the problem as a special case.