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

using i32 = int;
using i64 = long long;
using i128 = __int128_t;
using f64 = double;
using p2 = pair<i64, i64>;
using el = tuple<i64, i64, i64>;
using mint = atcoder::modint;

void _main();
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(18);
  _main();
}

void _main() {
  i64 tt;
  cin >> tt;
  for (;tt--;) {
    i64 n, k;
    cin >> n >> k;
    i64 ans = 1e18;
    vector<i64> a(n);
    i64 s = 1;
    for (i64 i = 0; i < n; i++) {
      cin >> a[i];
      s *= a[i];
    }
    for (i64 i = 0; i < n; i++) {
      ans = min(ans, s / a[i] * (a[i] - k));
    }
    cout << ans << "\n";
  }
}