PLEASE HELP!!!!

Wisconsin used to issue six-character license plates which began with three letters followed by three
numbers, zero to nine. Of the 26 letters in the alphabet, only 23 are used on the standard plates; I, O
and Q are not used because they resemble numbers. How many different license plates were
available to residents of Wisconsin?

2.
In how many ways can you arrange 9 different books on a shelf?

3.
In how many ways can a supermarket manager display 17 brands of cereal in 5 spaces on a shelf?