from collections import deque, defaultdict, Counter
from bisect import bisect_left, bisect_right
from itertools import permutations, combinations
from heapq import heappop, heappush
import math, sys
input = lambda: sys.stdin.readline().rstrip("\r\n")
_int = lambda x: int(x)-1
MOD = 998244353 #10**9+7
INF = 1<<60
Yes, No = "Yes", "No"

for _ in range(int(input())):
    N, K = map(int, input().split())
    A = list(map(int, input().split()))
    ans = INF
    for si in range(N):
        cnt = 1
        for i in range(N):
            if si == i:
                cnt *= (A[i]-K)
            else:
                cnt *= A[i]
        ans = min(ans, cnt)
    print(ans)