There are two bookshelves, A and B. Shelf A has $$1100$$ books, and shelf B has books $$300$$. We need to take  books from shelf A to shelf B, so that books in shelf B is three times more than self A. 
选项为:A:$$750$$  B:$$800$$  C:$$850$$  D:$$900$$  请回答其中一个选项.