T=int(input())
for _ in range(T):
    N,K=map(int,input().split())
    A=list(map(int,input().split()))
    ans=1<<30
    for i in range(N):
        tmp=1
        for j in range(N):
            if j==i:tmp*=A[j]-K
            else:tmp*=A[j]
        ans=min(ans,tmp)
    print(ans)