#include <iostream>
#include <cstdio>
#include <vector> 
#include <cstring>
#include <algorithm>
using namespace std;

const int N = 1e5 + 100;

int a[N];

int main(){
    int T;
    cin >> T;
    while (T --){
        int n;
        cin >> n;
        for (int i = 1; i <= n; i ++) scanf("%d", &a[i]);
        sort(a + 1, a + n + 1);
        long long ans = 0;
        for (int i = 1; i < n; i ++){
            ans += 1LL * (a[i + 1] - a[i]) * i * (n - i);
        }
        cout << ans << endl;
    } 
}