Try this problem from Test of Mathematics, TOMATO Objective problem number 44, useful for ISI B.Stat and B.Math.
Problem: TOMATO Objective 44
Suppose that (n> 2) are real numbers such that x for . Consider the sum where the summations are taken over all i, j, k: and i, j, k are all distinct. Then S equals:
(A) ; (B) (n-3)(n-4); (C) (n-3)(n-4)(n-5); (D) none of the foregoing expressions;
Hence option D