A personal identification number may be set to be any 4 digits. (a) How many possible PINs are there? (b) How many possible PINs are there that do

  1. A personal identification number may be set to be any 4 digits.
  2. (a) How many possible PINs are there?
  3. (b) How many possible PINs are there that do not have a repeated digit? (c) How many possible PINs are there that do have a repeated digit?