// Online C++ compiler to run C++ program online
#include <iostream>
#include <vector>
using namespace std;

void solve()
{
    int n, k;
    cin >> n >> k;
    vector<int> v(n);

    long long prod = 1;
    for (auto &i : v)
    {
        cin >> i;
        prod *= i;
    }

    // cout << prod << endl;

    long long mini = 1e10;
    for (auto &i : v)
        mini = min((prod / i) * (i - k), mini);

    cout << mini << endl;
}

int main()
{
    int t = 1;
    cin >> t;
    while (t--)
        solve();

    return 0;
}