4. Recall the problem of finding the number of inversions. We are given an array A[1..n] of n num- bers, which we assume are all distinct, and we define an inversion to be a pair i A[j]. The problem is to count the number of inversions in A. Let's call a pair (i, j) is a significant inversion if i 2A[j]. Give an O(n log n) algorithm to count the number of significant inversions in A