Answer: Rs 150 profit.
Step-by-step explanation: if 10 books went for Rs 40 each, you multiply 10 by 40 to get Rs 400. Then you subtract 10 books from 40 books to get 30 books which were the remaining ones that went for Rs 45 each. You then have to multiply 30 by 45 to get Rs 1350 for 30 books which you will then add to Rs 400 to get Rs 1750 which was the total amount of money all the books went for. You can now then subtract Rs 1600 from Rs 1750 to get Rs 150 which was the profit made.
