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Question 2: In a certain system, passwords consist of 8 characters. The first three characters are uppercase letters (A through Z), the next two characters are digits (0 through 9), and the last three characters are lowercase letters (a through z). Therefore, a password can be any string of the form:Letter-Letter-Letter-Digit-Digit-Letter-Letter-Letter. a) How many different passwords are possible? There are 26 uppercase letters (A through Z), 10 digits (0 through 9), and There are 26 lowercase letters (a through z). b) How many different passwords are possible if no digit appears more than once? c) How many different passwords are possible if no letter or digit appears more than once?

          Question 2: In a certain system, passwords consist of 8 characters. The first three characters are uppercase letters (A through Z), the next two characters are digits (0 through 9), and the last three characters are lowercase letters (a through z). Therefore, a password can be any string of the form:Letter-Letter-Letter-Digit-Digit-Letter-Letter-Letter.
a) How many different passwords are possible? 
 There are 26 uppercase letters  (A through Z), 10 digits  (0 through 9), and   There are 26 lowercase letters (a through z).
b) How many different passwords are possible if no digit appears more than once? 
c) How many different passwords are possible if no letter or digit appears more than once?

Added by Vicente B.

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