我有一个朋友一年多前遭遇车祸，现在正与对方保险公司交涉理赔事宜，对方已承认全责。我那位朋友提出索赔medical bill 的15倍(好像在美国一般是10-20倍吧...)，对方出offer数额为 medical bill 的大约五倍，现开始 negotiation，双方都 understand that if a lawyer is involved, then a substantal percentage of the compensation is gone, and if possible, would like to settle on the amount so they can pay less and my friend can get more.
问题：In this case, between 15 times and 5 times, what would be a good bottom line (i.e., as long as it's equal or above, we can accept)?
Also, what would be a good "counter" (i.e., higher than the bottom line but still makes sense so the negotiation can go on)?
