A wholesaler bought 2100 books for Tk.20 each. The wholesaler sold 50 percent of the books for Tk.35 each and the rest for Tk.18 each. What was the wholesaler's average profit per book?

প্রশ্নঃ A wholesaler bought 2100 books for Tk.20 each. The wholesaler sold 50 percent of the books for Tk.35 each and the rest for Tk.18 each. What was the wholesaler's average profit per book?