Question 1059577
You have 3 subjects, so 3! 
Then you have Economics, there are 4 ways to do this. But since they have to stay together but not in any particular order, consider the 4 books as 1 "lump" or 1 big book. So, we have 1+3+4 = 8 books and we can arrange them in 8! ways (See? by calling the Economics books 1 we always keep them together).
So now we have 3!8! = 241,920 ways to arrange the books, always keeping the Economics books together.