P4 [20 points] SUBSET-SUM: Given a set S of n non-negative integers, does there exist a subset of k of the integers that sums to a value c ? We know that SUBSET-SUM is NP-complete. HALF-PARTITION: Given a set S of n non-negative integers, does there exist a partition of S into subsets X and Y such that XY=S,XY= the sum of the integers in X equals the sum of the integers in Y ? Prove that HALF-PARTITION is NP-complete