#ifdef ONPC
#define _GLIBCXX_DEBUG
#endif
#include <bits/stdc++.h>
#ifdef ONPC
#include "debug.hpp"
#else
#define debug(...) 42
#endif
using namespace std;
#define int long long
#define nl "\n"

void solve()
{
    int n, k;
    cin >> n >> k;
    vector<int> a(n);
    for (int &val : a)
    {
        cin >> val;
    }
    int curr = 1;
    for (int i = 0; i < n; ++i)
    {
        curr *= a[i];
    }
    int mini = LLONG_MAX;
    for (int i = 0; i < n; ++i)
    {
        int temp = curr / a[i];
        mini = min(mini, temp * (max(0ll, a[i] - k)));
    }
    cout << mini << nl;
}

int32_t main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    int t = 1;
    cin >> t;
    for (int i = 0; i < t; ++i)
    {
        debug(i);
        solve();
    }
    return 0;
}