#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for (int i = 0; i < (n); ++i)
using ll = long long;
using ull = unsigned long long;

int main() {
  cin.tie(nullptr)->sync_with_stdio(false);
  int t;
  cin >> t;
  while (t--) {
    int n, k;
    cin >> n >> k;
    vector<ll> a(n);
    rep(i, n) cin >> a[i];
    const ll prd = accumulate(a.begin(), a.end(), 1LL, [](ll ac, ll x) {
      return ac * x;
    });
    ll ans = 1e18;
    rep(i, n) ans = min(ans, prd / a[i] * (a[i] - k));
    cout << ans << '\n';
  }
  return 0;
}