3.37: 6-character passwords from letters, numbers and symbols
A 6-character password is to be formed from the letters b, f, g, k, m; the numbers 3, 5, 7, 9; and the symbols , , . Each character can be used at most once.
(a)[1]
Find the number of 6-character passwords that can be formed if there are no further restrictions.
(b)[2]
Find the number of 6-character passwords that can be formed if the password starts and ends with a symbol.
(c)[2]
Find the number of 6-character passwords that can be formed if the password starts with either a symbol then a number, or a number then a symbol, and ends with 2 letters.