#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

const ll INF = 1e18;
const int MOD = 1e9 + 7;

int main() {
    int t;cin>>t;
    while(t--){
        ll n,k;cin>>n>>k;
        vector<ll> v(n);
        for(auto &a:v) cin>>a;
        sort(v.begin(),v.end());
        v[0] -= k;
        ll ans = v[0];
        for(int i=1;i<n;i++){
            ans *=v[i]; 
        }
        cout<<ans<<endl;
    }
   
    return 0;
}