How many different keys can be made for a lock that has 4 tumblers with 4 possible heights each?

If we are to add up the number of items presented in this given, we will have the answer of 8. The number of lock that can be made out of these items is calculated by the number of ways that these can be arranged which is determined by the number's factorial.
     N  = 8! 
The numerical equivalent is 40,320.

ANSWER: 40,320.