#include <bits/stdc++.h>

using namespace std;
#define ll long long
static const long long MOD = 1000000007;
static const int MAXN = 1000000; // adjust as
ll inf = 1e17;
ll f(ll x, ll num) {
  if (num > x) return x + 1;
  else if (num == x) return x;
  else return x-  1;
}
ll power(ll base, ll exp) {
    ll res = 1;
    base %= MOD;
    while (exp > 0) {
        if (exp % 2 == 1) res = (res * base) % MOD;
        base = (base * base) % MOD;
        exp /= 2;
    }
    return res;
}


void solve() {
  ll n, k;
  cin >> n >> k;
  vector<ll>arr(n);
  ll num = 1;
  for (ll i = 0; i < n; i++) {
    cin >> arr[i];
    num *= arr[i];
  }
  ll mini = LLONG_MAX;
  for (ll i = 0; i < n; i++) {
    ll temp= num;
    temp /= arr[i];
    temp *= (arr[i] - k);
    mini = min(mini, temp);
  }
  cout << mini << endl;


   





}
 



int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
  
  

   
    int t;
    cin >> t;
    while (t--)
    {
        solve();
    }
    
    //solve();

    return 0;
}