Let A = {a, b, c, d}. Find the number of 3-combinations of A where repetition of symbols is allowed.

list the days during the next 60 days on which megan and michele will see each other in city b

A 100-page document is being printed by four printers. Each page will be printed exactly once. Suppose that the first and the last page of the document must be printed in color, and only two printers are able to print in color. The two color printers can also print black-and-white. How many ways are there for the 100 pages to be assigned to the four printers. Hint: Use the product rule.

How did you get the values in the able?