Could you tell me the book with published price more than 4000000?
select t1.title from book as t1 join publication as t2 on t1.book_id = t2.book_id where t2.price > 4000000
Who were their writers?
select t1.writer from book as t1 join publication as t2 on t1.book_id = t2.book_id where t2.price > 4000000