Solution: There are 26 ways to choose the first letter(you can put any letter of the aphabet on the first place). The same for the rest except the last. There is the only way to choose the last letter.
In this way there are 26 ways to choose a letter for each place from the first to the seventh:
n = 26*26*26*26*26*26*26*1 = 8 031 810 176
Answer: 8 031 810 176.
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