Show that there are C(n + r - ql - q2 - . . . - qr -I, n -
Chapter 5, Problem 5.5.28(choose chapter or problem)
Show that there are C(n + r - ql - q2 - . . . - qr -I, n - ql - q2 - ... - qr ) different unordered selections of n objects of r different types that include at least ql objects of type one, q2 objects of type two, ... , and qr objects of type r .
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