Give the author's name of the books that cost 19 dollars and above.
books cost 19 dollars and above refers to price > = 19
SELECT DISTINCT T3.author_name FROM book AS T1 INNER JOIN book_author AS T2 ON T1.book_id = T2.book_id INNER JOIN author AS T3 ON T3.author_id = T2.author_id INNER JOIN order_line AS T4 ON T4.book_id = T1.book_id WHERE T4.price > 19