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