t = int(input())

for _ in range(t):
    n, k = map(int, input().split())
    a = list(map(int, input().split()))
    ans = float('inf')
    t = list(range(n))
    for i in range(n):
        total = 1
        for j in range(n):
            if i == j:
                total *= (a[j] - k)
            else:
                total *= a[j]
                
        ans = min(ans, total)

    print(ans)