21. Combinatorics and Probability

How many possible outcomes are there if you roll 5 dice?

How many options are there for license plates with any three letters (A-Z) followed by any 3 numbers (0-9)?

Phone numbers are 10 digits long. How many possible phone numbers are there if the 1^st and 4^th numbers can't be 0?

A student formed a club at their school. They have 13 members, and need to elect a president, vice president, and treasurer. How many ways are there to fill these officer positions?