https://blog.gongquiz.com/2022/11/12/60cu-40zn-%ed%99%a9%eb%8f%99%ec%9c%bc%eb%a1%9c-%eb%b3%b5%ec%88%98%ea%b8%b0%ec%9a%a9-%ed%8c%90-%eb%b3%bc%ed%8a%b8-%eb%84%88%ed%8a%b8-%eb%93%b1%ec%97%90-%ec%82%ac%ec%9a%a9%eb%90%98%eb%8a%94/