for _ in range(int(input())):
    ans = 1 << 80
    n, k = list(map(int, input().split()))
    A = list(map(int, input().split()))
    for i in range(n):
        t = 1
        for j in range(n):
            if i == j:
                t *= A[j]-k
            else:
                t *= A[j]
        ans = min(ans, t)
    print(ans)