#include<bits/stdc++.h>
#define ll long long
using namespace std;
int T,n,a[100005];
ll ans;

int read(){
    int x=0;char ch=getchar();
    while(!isdigit(ch)) ch=getchar();
    while(isdigit(ch)) x=(x<<3)+(x<<1)+(ch^48),ch=getchar();
    return x;
}

void print(ll x){
    if(x>=10) print(x/10);
    putchar(x%10+'0');
}

int main(){
    T=read();
    while(T--){
        n=read();
        for(int i=1;i<=n;i++) a[i]=read();
        sort(a+1,a+n+1);
        ans=0;
        for(int i=1;i<n;i++) ans+=1ll*(a[i+1]-a[i])*i*(n-i);
        print(ans),puts("");
    }

    return 0;
}