Imagine you are managing a database for a bookstore. The table book$\_$sales contains information about sales transactions. Each row represents a sale, including the book's title, the quantity sold, the sale date, and the total revenue generated. Your task is to write a query that retrieves the books that have a total quantity sold greater than $50$ and an average revenue per book greater than $$15.$

The average Revenue generated should be rounded to two decimal places.

Output the results in descending order of average revenue per book.

Tables Schema as Below:

book$\_$sales

columnName dataType

sale$\_$id INT

book$\_$title VARCHAR$(255)$

quantity$\_$sold INT

sale$\_$date DATE

total$\_$revenue INT