#include <bits/stdc++.h>
using std::cin;
using std::cout;

typedef long long ll;

int n;
int a[100054];

void work() {
    int i; ll ans = 0;
    cin >> n;
    for (i = 0; i < n; ++i) cin >> a[i];
    std::sort(a, a + n);
    for (i = 1; i < n; ++i)
        ans += ll(a[i] - a[i - 1]) * i * (n - i);
    cout << ans << '\n';
}

int main() {
    int T;
    std::ios::sync_with_stdio(false), cin.tie(NULL);
    for (cin >> T; T; --T) work();
    return 0;
}