#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

int main() {
    cin.tie(0);
    ios_base::sync_with_stdio(false);
    int t;
    cin >> t;
    while (t--) {
        int n;
        cin >> n;
        vector<ll> a(n);
        for (int i = 0; i < n; i++) {
            cin >> a[i];
        }
        sort(a.begin(), a.end());
        ll res = 0, cnt = 0;
        for (int i = 0; i < n-1; i++) {
            cnt += n-1-i;
            res += cnt*(a[i+1]-a[i]);
            cnt -= (i+1);
        }
        cout << res << endl;
    }
}