Draw 1) a context data flow diagram (level-0) and 2) a level-1 diagram that shows the appropriate details for the point of sales system described below:

Self-checkout system at Big Joes Supermarket uses a scanner to read universal product bar codes (UPC). When a customer scans a product, the system reads the barcode of the product, the product information is read by the system based on data stored in a product file. The system displays the product summary to the customer. When the customer provides payment information, and the system verifies the payment information by connecting to an external credit/banking verification system. Purchases made are stored in a file to be used in printing the receipt. After the purchase has been made a receipt is produced and given to the customer.