def solve():
    N, K = map(int, input().split())
    A = list(map(int, input().split()))

    ans = 10 ** 18
    for i in range(N):
        cost = 1
        for j in range(N):
            if j == i:
                cost *= A[j] - K
            else:
                cost *= A[j]

        ans = min(ans, cost)

    return ans

#==================================================
import sys
input = sys.stdin.readline
write = sys.stdout.write

T = int(input())
write("\n".join(map(str, [solve() for _ in range(T)])))