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-#Domain Models In Here
\ No newline at end of file
+#Domain Models In Here
+# Custom Domain Model
+
+### Scenario Excercise
+# Purchasing products
+```
+As a supermarket shopper,
+So that I can pay for products at checkout,
+I'd like to be able to know the total cost of items in my basket.
+```
+
+| Classes         | Methods                                     | Scenario               | Outputs |
+|-----------------|---------------------------------------------|------------------------|---------|
+| `Checkout` | `public double CalculateCost(List<Products> products)`  | If there are products in list | (double) Total sum of products  |
+|            |                                                  | If no products in list | 0     |
+|            |                                                  | If a product has invalid cost | -1  |
+|            | `bool Pay(Customer customer, double cost)`       | If customer can pay | true |
+|            |                                                  | If customer can't pay | false |
+
+# Receipt
+
+```
+As an organised individual,
+So that I can evaluate my shopping habits,
+I'd like to see an itemised receipt that includes the name and price of the products
+I bought as well as the quantity, and a total cost of my basket.
+```
+| Classes         | Methods                                     | Scenario               | Outputs |
+|-----------------|---------------------------------------------|------------------------|---------|
+| `Receipt` | `double CalculateCost(List<Products> products)`  |  |   |
+|            | 'string PrintReciept()'                         |  |                      | If list is empty | 0     |