#include <iostream>
using namespace std;

int main() {
    int T;
    cin >> T;
    while (T--) {
        int N, K;
        cin >> N >> K;
        long long A[10];
        for (int i = 0; i < N; i++) {
            cin >> A[i];}
        long long answer = -1;
        for (int i = 0; i < N; i++) {
            long long prod = 1;
            for (int j = 0; j < N; j++) {
                if (j == i)
                    prod *= (A[j] - K);
                else
                    prod *= A[j]; }
            if (answer == -1 || prod < answer)
                answer = prod;  }
        cout << answer << endl; }
    return 0;
}