Passage: A bookshop owner noticed that on the days when she set out a table of discounted books at the entrance, the total number of books she sold went up, but her total takings for the day were about the same as on ordinary days. Which of the following best explains this?

Takings equal price multiplied by quantity. Quantity rose while takings stayed flat, so the average price received per book must have fallen by an offsetting amount — exactly what discounting does. The other options either contradict the reported rise in sales or introduce facts the passage does not mention.