How many two-letter codes can be formed using the letters
Chapter 13, Problem 31(choose chapter or problem)
How many two-letter codes can be formed using the letters A, B, C, and D? Repeated letters are allowed.
Unfortunately, we don't have that question answered yet. But you can get it answered in just 5 hours by Logging in or Becoming a subscriber.
Becoming a subscriber
Or look for another answer