How is the zakat calculated for a commercial shop, as well as for books that have been sold and those that have not, knowing the price of the book and the price of one gram of gold?

If the books are owned with the intention of trading them, then they are considered trade goods. Zakat is obligatory on them if their value reaches the nisab, either by themselves or by combining them with money and other trade goods, and a full year (hawl) has passed over them. One-quarter of one-tenth (2.5%) of their value must be paid. The shop itself is not subject to zakat.