翻译,一句话.要人工.中译英.谢谢

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翻译,一句话.要人工.中译英.谢谢
Talk about the breakthroughs,not only was the building sturdy and fireproof but they were cheap to put up too.
我就是不知道后面这cheap to put up .啥意思- -~!

谈到这个(技术上)的突破,不仅是使建筑物结实且防火,而且建造成本低廉