It means that we need to arrange 11 elements from the multiset S, where there are 3 copies of 'a', 4 copies of 'b', and 5 copies of 'c'.
Now, let's use the formula for the number of permutations of a multiset:
$$
\frac{n!}{n_1!n_2!...n_k!}
$$
where n is the
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