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Explanation:
The word "combine" has three vowels o, i, and e.
One grouping of the three vowels together leads to oie, which we'll replace with Z for now.
So we have the "word" Zcmbn after taking out the vowels and replacing with Z temporarily. There are 5 letters in Zcmbn making 5! = 5*4*3*2*1 = 120 different permutations.
Within any permutation of Zcmbn, there are 3! = 3*2*1 = 6 ways to arrange the sequence oie
So overall there are 6*120 = 720 different ways to arrange the word "combine" such that all the vowels stick together.