Please kindly tell me in what normal forms (..., 3NF, BCNF, 4NF, 5NF, 6NF, etc.) (why, and how to maximally normalize) the following example of a "database" formed by solving the many-to-many relationship between the tables tbl_Books and tbl_Bookshops:

The [out_of_stock] field is of logical type (Yes/No).
tbl_Bookshops (bookshop_id, user_name)
tbl_Books (book_id, book_name, out_of_stock, sale_price)
tbl_Distributions (library_id, bookshop_id, cost_price)

Thank you in advance!