When laying out a computer system the monitor should be placed where?

It should be layed out so that when you sit in front of the desk the monitor should be elivated so top of the monitor's screen should be just above your eyebrows so your eyes get maximum view of the screen and on the the desk the keyboard should be on the desk in front of you placed at the length of where your arm are slightly bent and the monitor about 5cms behind the keyboard.