Answer:
solution given:
total alphabet =26
The first letter can be any one of the 26 letters in the alphabet.
so
1st word =26letter
since no word is repeated
2nd word =25letter
3rd word=24letter
4th word=23letter
four-letter code =26×25×25×23=358800codes
358800codes of four-letter codes can be made if no letter can be used twice.
There are 26 letters in the alphabet.
1st letter can be 1 of 26
2nd letter can be 1 of 25
3rd letter can be 1 of 24
4th letter can be 1 of 23
Total combinations = 26 x 25 x 24 x 23 = 358,800
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