Mr. Holmes has been getting his Master's in Education from Dowling College and has just heard the news: due to low enrollment, Dowling College will be closing! Because of this, there will be a sale at the campus bookstore and everything is 30% off. If he buys a hat with an original price of $25.00, he believes that the price will be $7.50. When he gets to the register however, the cashier tells Mr. Holmes that he owes $17.50. Who do you think is correct, Mr. Holmes or the cashier?