tokens: My shop sells both normal books and ebooks , and charge different rates of for shipping based on the subtotal of all items in the cart ( $7 shipping cost for subtotal of less than $20 , $14 shipping cost for between $20 and $ 50 .. etc ) .
ner_tags: O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O