(a) In a certain state, license plates consist of three letters (AZ) followed by three digits (09). How many different plates can be issued?
(b) If the state allows any six-character mix (in any order) of 26 letters and 10 digits, how many unique plates are possible?
(c) Why might some combinations of digits and letters be disallowed?
*(d) Would the system described in (b) permit a unique license number for every car in the United States? For every car in the world? Explain your assumptions.
*(e) If the letters O and I are not used because they look too much like the numerals 0 and 1, how many different plates can be issued?