#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)

int main(){
    int t;
    cin >> t;
    while(t--){
        int n,k;
        cin >> n >> k;
        vector<ll>a(n);
        rep(i,n)cin >> a[i];
        sort(a.begin(),a.end());
        a[0]-=k;
        ll ans=1;
        rep(i,n)ans*=a[i];
        cout << ans << endl;

    }
    return 0;
}