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## Example: Printing an Invoice (CRC Cards)

- To discover classes, list the nouns:

  > Invoice | Address | Item | Product | Description
  > Price | Quantity | Total | Amount Due |

- Note that Toaster is a data value for an Item object, not a class.
- Product description and price are fields of the Produce class.
- Quantity is not an attribute of a Product.
- We will create an Item class that records the product and the quantity ("3 toasters").
- Our four candidates for classes are:

  > Invoice | Address | Item | Product

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