6) Counting Password - Each character in a password is either a digit [0-9] or lowercase letter [a-z] or special characters [*, &, $, #]. How many valid passwords are there with the given restriction(s)?

a) Length 6. Characters can be special characters, digits, or letters

b) Length 7, 8, or 9. Characters can be special characters, digits, or letters

c) Length 7, 8, or 9. Characters can be special characters, digits, or letters. The first character cannot be a letter.