https://blog.gongquiz.com/2020/12/06/%ed%83%84%ec%86%8c-2kg%ec%9d%84-%ec%99%84%ec%a0%84%ec%97%b0%ec%86%8c%ec%8b%9c%ec%bc%b0%ec%9d%84-%eb%95%8c-%eb%b0%9c%ec%83%9d%eb%90%9c-%ec%97%b0%ec%86%8c%ea%b0%80%ec%8a%a4co2%ec%9d%98-%ec%96%91-2/