Explanation

Let's calculate the cost per book:

10 books = 240 rupees, so the cost per book is:

240 rupees ÷ 10 books = 24 rupees per book

To find the cost of 15 books, multiply the cost per book by 15:

24 rupees/book × 15 books = 360 rupees

So, the correct answer is: Rs. 360.