for _ in range(int(input())):
  n,k=[*map(int,input().split())]
  a=[*map(int,input().split())]
  ans=1<<60
  for i in range(n):
    na=1
    for j in range(n):
      if i!=j:
        na*=a[j]
      else:
        na*=a[j]-k
    ans=min(ans,na)
  print(ans)