#include <bits/stdc++.h>
using namespace std;
int t, n, m, p;
int a[123123];
int main() {
    scanf("%d", &t);
    while (t--) {
        scanf("%d", &n);
        for (int i = 1; i <= n; ++i) scanf("%d", &a[i]);
        sort(a + 1, a + n + 1);
        unsigned long long sum = 0, ans = 0;
        for (int i = 1; i <= n; ++i) {
            ans += 1ull * a[i] * (i - 1) - sum;    
            sum += a[i];
        }
        printf("%llu\n", ans);
    }
}