Calculate total amount order details

My applciations is for restaurants to order products from different and multiple suppliers. I have a catalogue with all the items from all sorts of suppliers. Restaurant owners can place an order and see the order details. I want the total amount of the items calculated into the order details.   And when suppliers receive an order they should only see the total amount of the products ordered at them.   Here is the domain model
1 answers


Perhaps this page can help you:

For calculation of totals: and

I think that when you read this page, you will get your answer on how to get the total amount of products per supplier.