In order to compare, you'd have to find out how much they paid for each pound of tri-tip. So, to do this, you would divide the total amount of money the spent on the pounds by the number of pounds they bought. So for Kevin, you'd divide 29.97 by 3 to get that Kevin paid $9.99 for each pound. For Arnold, you'd divide 35.96 by 4 to get that Arnold paid $8.99 for each pound. And 8.99 is less than 9.99, so Arnold was right.
Since a function would mean that a customer is able to purchase 1.1 of an item or 1.5 of an item, which is false. It also means that the customers pay the same price for a different amount of items.
