Passwords on an ancient computer are required to be 4-5
characters long and made up of lower case letters only (a..z :
there are 26 possibilities). Please answer each of these questions
below, giving numerical answers. You should also explain how you
got each answer, for full or partial credit.
a) Assume that letters may NOT be repeated, and passwords are
4-5 letters long. How many passwords are possible?
b) Assume that letters MAY be repeated, and passwords are 4-5...