#include <bits/stdc++.h>
#define ll long long
#define int long long
#define double long double
#define float double
#define pb push_back
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define nl '\n'
#define here cout << "HERE" << endl;
#define forn(i, a, n) for (int i = a; i < n; i++)
#define print(a) for (auto& e : a) cout << e << " "; cout << endl;
#define MOD(a, b) (((a) % (b) + (b)) % (b))
#define yesno(b) cout << ((b) ? "YES\n" : "NO\n")
#define fast ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
using namespace std;
using vi = vector<int>;
using pii = pair<int,int>;

// 10x20x30
// divide by 10 then mult by 10-5=5
void solve(){
    int n,k;
    cin>>n>>k;
    vi arr(n);
    int prod=1;
    forn(i,0,n){
        cin >> arr[i];
        prod*=arr[i];
    }
    int mn=LLONG_MAX;
    forn(i,0,n){
        int curr=prod/arr[i];
        curr*=(arr[i]-k);
        mn=min(mn,curr);
    }
    cout<<mn<<nl;
}

signed main(){
    fast
    //freopen("input.txt", "r", stdin);
    //freopen("output.txt", "w", stdout);
    int t = 1;
    cin >> t;
    for(int i=0;i<t;i++){ 
        // cout<<"Case "<<i+1<<": ";
        solve(); 
    }
    return 0;
}