Class b and class C. Guo Song Branch is a 20 18 branch of Changsha Library, which is a public welfare library open to the society. It was jointly built by Changsha Library, Wangcheng District Library and other units and social forces. Books are collected from two-level public libraries. According to the data, Guo Song Branch of Changsha Library charges in six grades: 50 yuan, B 1, 200 yuan, 300 yuan, 50 yuan and C2. The deposit is different, and the number of books borrowed is different. B-level books can be borrowed from C-level books, that is, adult books, children's books, periodicals and CDs, while C-level books can only be borrowed from children.