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

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int T;
    cin >> T;
    while(T--){
        int n, k;
        cin >> n >> k;
        vector<int> a(n);
        ll v = 1, ans = 1ll << 60;
        for(int i = 0; i < n; i++){
            cin >> a[i];
            v *= a[i];
        }
        for(int i = 0; i < n; i++){
            ans = min(ans, v / a[i] * (a[i] - k));
        }
        cout << ans << '\n';
    }
}