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

void solve(){
  int n,k;
  cin>>n>>k;
  vector<int> a(n);
  long long ans=1;
  int m=2e9;
  for (int i=0;i<n;i++){
    cin>>a[i];
    ans*=a[i];
    m=min(m,a[i]);
  }
  ans/=m;
  ans*=m-k;
  cout<<ans<<endl;
}

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