for _ in range(int(input())):
    n, k = map(int,input().split())
    a = list(map(int,input().split()))
    p = 1
    for i in range(n): p *= a[i]
    mn = p
    for i in range(n):
        p //= a[i]
        p *= (a[i] - k)
        mn = min(mn, p)
        p //= (a[i] - k)
        p *= a[i]
    print(mn)