阅读理解提问the freezing point of one liter of antifreeze and one liter of water

阅读理解提问the freezing point of one liter of antifreeze and one liter of water mixed together is ()零下24°，零下22°，零下20°，零下18°应该怎么选呢？文章只给出了防冻剂的结冰点和水的结冰点，能得出他们分别一公斤混合起来之后的结冰点吗？且文章只给出5部分的水4部分的防冻剂，部分和公斤有单位可以换算吗？求详细讲解Water freezes at 0℃；the usual kind of antifreeze will not freeze until the temperature is －40℃. A mixture(混合物) of five parts of water and four parts of antifreeze will prevent freezing at－18℃；four parts of water and five parts of antifreeze reduce this to －22℃.

零下22°

理由是：
最后一句说，four parts of water and five parts of antifreeze reduce this to －22℃.
两种东西的量相等时，即4：4时，结冰点是-22°C。
所以1升水和1升防冻剂量相等，也应该是零下22°结冰。