hi..NP complete problem...Urgent..

I have a finite Set A, consisting of integers. You have an integer k and a bound 'B'

Prove that the partitioning of set A into 'k' disjoint sets such that

Sum from 1 to k { {sum of each disjoint set} squared } <= B

is NP complete.

This problem is actually the MINIMUM SUM OF SQUARES PROBLEM:-

MINIMUM SUM OF SQUARES

I know that we need to reduce it from the PARTITION problem, but Im not sure how to proceed..

I urgently need the answer and I have been trying real hard but with no luck..

Thank you all for your help guys,