T = int(input())

for _ in range(T):
    N, K = map(int, input().split())
    A = list(map(int, input().split()))

    ans = 1 << 60
    for i in range(N):
        tmp = 1
        for j in range(N):
            if j == i:
                tmp *= A[j] - K
            else:
                tmp *= A[j]
        ans = min(ans, tmp)

    print(ans)