for _ in range(int(input())):
    N, K = map(int, input().split())
    A = list(map(int, input().split()))

    ans = 1<<60
    for i in range(N):
        SUM = 1
        for j in range(N):
            if i == j:
                SUM *= A[j]-K
            else:
                SUM *= A[j]
        ans = min(ans, SUM)
    
    print(ans)