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

int main(){
    int t;
    cin >> t;
    for(;t--;){
        int n, k;
        cin >> n >> k;
        vector<int> a(n);
        ll s = 1;
        for(int i = 0; i < n; i++){
            cin >> a[i];
            s *= a[i];
        }

        ll ans = 1e18;
        for(int i = 0; i < n; i++){
            ll cal = s / a[i];
            cal *= (a[i]-k);

            ans = min(ans, cal);
        }
        cout << ans << endl;
    }
    return 0;
}