UPSC NDA Math Model Paper 3

Given, There are 4 books on fairy tales, 5 novels and 3 plays.
Here, books are arranged in the order, books on fairy tales, novels and then plays.
There are 4 books on fairy tales and they have to be put together. They can be arranged in 4! ways.
There are 5 novels. They can be arranged in 5! ways.
And there are 3 plays. They can be arranged in 3! ways.
So, by the counting principle all of them together can be arranged in 4!´5!´3! ways = 17280