#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>

#include <atcoder/all>
#define rep(i, a, b) for (ll i = (ll)(a); i < (ll)(b); i++)
using namespace atcoder;
using namespace std;

typedef long long ll;

void solve() {
    int n, k;
    cin >> n >> k;
    vector<int> a(n);
    rep(i, 0, n) cin >> a[i];
    ll sm = 1;
    rep(i, 0, n) sm *= a[i];
    ll ans = 1e18;
    rep(i, 0, n) { ans = min(ans, sm / a[i] * (a[i] - k)); }
    cout << ans << '\n';
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(15);
    int t;
    cin >> t;
    while (t--) solve();
}