#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long long int lli;
#define pb push_back
#define MOD 1000000007
int main(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int t;cin>>t;
while(t--){
int n,m;cin>>n>>m;
vector<int> a(n*m);
for(int i=0;i<(n*m);i++) cin>>a[i];
sort(a.begin(),a.end());
int y= a[(n*m)-1]-a[0];
int x = max( (a[(n*m)-1]-a[1]) , (a[(n*m)-2]-a[0]) );
int ans= max( (x*(m-1) + y*m*(n-1)) , (x*(n-1) + y*n*(m-1)) );
cout<<ans<<endl;
}
}
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