Problem:

A Canadian postal code uses six characters. The first, third, and fifth are letters, while the second, forth, and sixth are digits. A U.S.A. zip code contains five characters, all digits.

How many codes are possible for each country?

Comments:

I'm stuck on this problem...actually I don't understand the 'Permutations and Organized Counting' unit at all... Anyway, can someone please help me with this question?