Ten books are arranged in a row on a shelf. How many ways can this be done if one particular book A must always be to the left, but not necessarily immediately to the left, of another book B?
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import itertools
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books = 'ABCDEFGHIJ'
total = 0
correct_perm = 0
for perm in itertools.permutations(books):
total += 1
if perm.index('A') < perm.index('B'):
correct_perm += 1
print(correct_perm)
print(total)
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