Basically I need to find a transfter function (Xi/Xu) but I am stuck with this 'c', no matter what I do I can't seem to get rid of it.
Another point is that I don't see how I will get 'Xi' into the equation, since there is no feedback from it so none of the signals (letters) have Xi in them....
Please offer an algebric solution if possible. I don't ask you to solve everything just to get me started.