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

#define int long long
#define vi vector<int>
#define vc vector<char>
#define vs vector<string>
#define vb vector<bool>
#define vpii vector<pair<int, int>>
#define vpic vector<pair<int, char>>
#define vpis vector<pair<int, string>>
#define vvi vector<vector<int>>
#define pb push_back
#define pii pair<int, int>
#define vvpii vector<vector<pair<int, int>>>
#define rep(i, s, e) for (int i = (s); i < (e); i++)
#define all(x) x.begin(), x.end()
#define fastio ios::sync_with_stdio(false); cin.tie(0);
#define MOD 1000000007
#define endl "\n"

signed main() {
    fastio;
    int t;
    cin >> t;
    while(t--) {
        int n, k;
        cin >> n >> k;
        vi v(n);
        int prod = 1;
        rep(i, 0, n) {
            cin >> v[i];
            prod *= v[i];
        }
        int ans = prod;
        rep(i, 0, n) {
            ans = min(ans, (prod / v[i]) * (v[i] - k));
        }
        cout << ans << endl;
    }
}