Answer:
456,796 passwords
Explanation:
Because any letter can be repeated for the 4-letter password, there are 26 possible letters for the first letter of the password, 26 possible letters for the second letter of the password, 26 possible letters for the third letter of the password, and 26 possible letters for the fourth letter of the password. Therefore, the possible number of passwords that can be created is 26*26*26*26 = 26^4 = 456,796 passwords