Need help please , Im a noob!

I want an example of calculating promotion that contains list of purchases each brand brands have promotion with service factory

Robot, this seems more like a generic angular query. Looking at this and your other queries Iā€™d suggest perhaps that you have go at following this tutorial and if you have further issues that you try to be more explanatory in your requests and, if possible, put together some CodePens to help other users help you.