import java.util.Arrays;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) throws Exception {
		Scanner sc = new Scanner(System.in);
		int t = sc.nextInt();
		for (int z = 0; z < t; z++) {
			int n = sc.nextInt();
			int k = sc.nextInt();
			int[] a = new int[n];
			for (int i = 0; i < n; i++) {
				a[i] = sc.nextInt();
			}
			Arrays.sort(a);

			a[0] -= k;
			long ans = 1;
			for (int i = 0; i < n; i++) {
				ans *= a[i];
			}
			System.out.println(ans);
		}
		sc.close();
	}
}