How many different quadruples can one form from the objects
1, 1, 2, 3, 4, 5, 6, 7, 8, 9.
Two quadruples differing only in order are not considered different.
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${8 \choose 4}+{8 \choose 3}+{8 \choose 2}$
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$10\cdot9\cdot8\cdot7$
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