It's just like the riddle, how many 책 can 당신 put on an empty shelf XD Need to think outside the box, i 사랑 riddles XD Right my work here is done, i shall possibly talk to 당신 soon
Once 당신 put a book into a empty bag, it is no longer empty. If you're asking how many 책 would fit into an empty bag, that depends on the size of 책 and the bag. :)
I read "the contest is done the answer is ONE BOOK BECAUSE IT WON'T BE EMPTY AFTER THIS" in the 코멘트 and I am going to disagree, 당신 can fit 2, 3, 4, 또는 more, just as long as 당신 put them all in at the same time.