24. Stones are numbered 1, 2, 3, 4, 5, 6, 7, 8, 9, 10. Three groups of stones can be selected
so that the sum of each group is 11. For example, one arrangement is
{1,10},
{2,3, 6},
{4,7}. Including the example, how many arrangements are possible?
(A) 13 (B) 16 (C) 11 (D) 12 (E) 15
W
3
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