#include<bits/stdc++.h>
#include<map>
using namespace std;
#define int long long
#define forn(i, a, b) for (int i = a; i < b; i++)
#define vect vector<int>
#define srt(vec) sort(vec.begin(),vec.end())
bool prime(int a)
{
if(a<=1||a%2==0||a%3==0)return 0;
for(int j=5; j*j<=a; j+=6) {
int k=j+2;
if(a%j==0||a%k==0)return 0;
}
return 1;
}
const int N=2e7+10;
//vector<int> vec(N);
void solve()
{
int n,k;
cin>>n>>k;
vect vec(n);
for(int &j:vec)
cin>>j;
srt(vec);
vec[0]-=k;
int sum=1;
forn(j,0,n)
sum*=vec[j];
cout<<sum<<endl;
}
signed main()
{
ios::sync_with_stdio(0);
cin.tie(0);

int t = 1;  
cin >> t;;  
    while (t--)  
        solve();  

    return 0;  
}