Hi Shuwen form Carrollton, TX.
First of all, I am sorry I missed your question back in September. I did not see it until today.
Perhaps you have already answered this or handed in your assignment. If you have I am sorry I did not see it, but I certainly would have been very glad to assist with your question.
If you would still like some assistance, contact me by my Wyzant email address. Click on my name and I can certainly help you and give you some very specific information pertaining to the question you asked.
Again, sorry I did not see this sooner.