/* -*- coding: utf-8 -*-
 *
 * 3433.cc:  No.3433 [Cherry 8th Tune A] ADD OIL! - yukicoder
 */

#include<cstdio>
#include<algorithm>

using namespace std;

/* constant */

const int MAX_N = 8;

/* typedef */

using ll = long long;

/* global variables */

int as[MAX_N];

/* subroutines */

/* main */

int main() {
  int tn;
  scanf("%d", &tn);

  while (tn--) {
    int n, k;
    scanf("%d%d", &n, &k);
    for (int i = 0; i < n; i++) scanf("%d", as + i);

    ll p = 1;
    for (int i = 0; i < n; i++) p *= as[i];
    ll minp = p;
    for (int i = 0; i < n; i++) {
      ll pi = p / as[i] * (as[i] - k);
      minp = min(minp, pi);
    }

    printf("%lld\n", minp);
  }

  return 0;
}