# https://yukicoder.me/problems/no/3433

def solve(N, K, A):
    answer = float("inf")
    for target_i in range(N):
        ans = 1
        for i in range(N):
            if i == target_i:
                ans *= (A[i] - K)
            else:
                ans *= A[i]
        answer = min(answer ,ans)
    return answer
        


def main():
    T = int(input())
    answers = []
    for _ in range(T):
        N, K = map(int ,input().split())
        A = list(map(int ,input().split()))
        ans = solve(N, K, A)
        answers.append(ans)

    for ans in answers:
        print(ans)





if __name__ == "__main__":
    main()