t = int(input())


def solve():
    n, k = map(int, input().split())

    arr = list(map(int, input().split()))

    pre = [1] * (n + 3)
    suf = [1] * (n + 3)

    for i in range(n):
        pre[i + 1] = pre[i] * arr[i]

        suf[n - i] = suf[n - i + 1] * arr[n - i - 1]

    ans = float("inf")

    for i in range(n):

        ans = min(ans, pre[i] * suf[i + 2] * (arr[i] - k))
    print(ans)

while t:


    solve()

    t -= 1



# adakldajdald