//Bismillah
#include <bits/stdc++.h>
using namespace std;
#define int long long int
#define f(i, a, n) for (int i = a; i < n; i++)
#define pr(vec) {for(auto &value: vec) cout<<value<<" ";} nl;
#define iv(vec) for(auto &value: vec) cin>>value;
#define pb push_back
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define uset unordered_set
#define mset unordered_multiset
#define vb vector<bool>
#define vi vector<int>
#define vvi vector<vector<int>>
#define vc vector<char>
#define vs vector<string>
#define vpii vector<pair<int,int>>
#define ld long double
#define nl cout<<"\n";
#define ned ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);int tt = 1;
#define yes cout << "YES\n"
#define no cout << "NO\n"
const int inf=1e17+1;
const int mod=32768;
void solve(){
    int n,k;cin>>n>>k;
    vi a(n);iv(a);
    int prod=1;
    for(int i=0;i<n;++i){
        prod*=a[i];
    }
    int mn=prod;
    for(int i=0;i<n;++i){
        int temp=prod/a[i];
        temp*=(a[i]-k);
        mn=min(mn,temp);
    }
    cout<<mn<<endl;
}

signed main(){
    ned;
    cin>>tt;
    while(tt--)
    {
        solve();
    }
    return 0;
}