A certain state’s auto license plates have three letters of the alphabet followed by a three-digit number.
a. How many different license plates are possible if all three-letter sequences are permitted and any number from 000 to 999 is allowed?
b. Arnold witnessed a hit-and-run accident. He knows that the first letter on the license plate of the offender’s car was a B, that the second letter was an O or a Q, and that the last number was a5. How many of this state’s a license plate fit this description?