How Many 3-letter Words Can Be Formed Using The 26 Letters Of The Alphabet If Repetition Of Letters Is Allowed Or Is Not Allowed?

How Many 3-letter Words Can Be Formed Using The 26 Letters Of The Alphabet If Repetition Of Letters Is Allowed Or Is Not Allowed? How many 3-letter words can be formed using the 26 letters of the alphabet if repetition of letters is allowed or is not allowed? (a) Repetition is allowed. The letters A-Z