#include <bits/stdc++.h>

using namespace std;

#define int long long int
#define ld long double
#define vi vector<int>
#define pii pair<int, int>
#define vpii vector<pair<int, int>>

#define all(a) a.begin(), a.end()
#define popc __builtin_popcountll
#define nl cout << endl;
#define yesno(a) cout << ((a) ? "YES": "NO");
#define here cout << "here" << endl;
const int inf = 1e17 + 1;

int gcd(int a, int b) { return !b ? a : gcd(b, a % b); }
int lcm(int a, int b) { return (a / gcd(a, b)) * b; }

template <typename T>
void input(vector<T>& arr) {
    for(int i = 0; i < arr.size(); ++i) {
        cin >> arr[i];
    }
}

void solve() {
    int n, k;
    cin >> n >> k;

    vi arr(n);
    input(arr);

    sort(all(arr));
    int ans = arr[0] - k;
    for(int i = 1; i < n; ++i) {
        ans *= arr[i];
    }
    cout << ans;
}

signed main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    // freopen("input.txt", "r", stdin);
    // freopen("output.txt", "w", stdout);

    int t = 1;
    cin >> t;
    for(int i = 1; i < t + 1; ++i) {
        // cout << "Case " << i << ": ";
        solve();
        nl
    }

    return 0;
}