Original sentence: A customer that is able to test the system every three weeks according to the functional requirements (User Stories).According to the views propounded, communication is important, but more important is what is communicated to whom and when.Again according to the views propounded, simplicity is about always choosing the simplest solution.Extreme Programming claims to be based on four values that provide both commercial and human needs.Feedback from the customer: The functional tests are written by the customer and the testers.Feedback from the system: by writing unit tests the programmers have direct feedback from of the state of the system after implementing changes.Feedback from the team: When customers come up with new requirements in the planning game the team directly gives an estimation of the time that it will take to implement.Related to the previous value, "communication", simplicity in your design and coding will improve the (quality of) communication.The Extreme Programming doctrine of "Courage in system development" can be best explained by a couple of practices.The four variables are:.Within eXtreme Programming, feedback is related to different dimensions of the system development:
Edited sentence: ( This article[LINK] refers to the importance of sleep for the brains).A customer that is able to test the system every three weeks according to the functional requirements (User Stories) ….By writing unit tests the programmers have direct feedback from of the state of the system after implementing changes.Communication is important, but more important is what is communicated to whom and when.Courage in system development can be best explained by a couple of practices.Extreme Programming is based on four values that provide both commercial and human needs.Related to the previous value “communication”, simplicity in your design and coding will improve the (quality of) communication.Simplicity is about always choosing the simplest solution.The four variables are.The functional tests are written by the customer and the testers.When customers come up with new requirements in the planning game the team directly gives an estimation of the time that it will take to implement.Within eXtreme Programming feedback is related to different dimensions of the system development:.•	Feedback from the customer.•	Feedback from the system.•	Feedback from the team