Then comes a final system, which is the point O is fixed on the body, but now it is, but although point O is fixed on the body, remember O X dash, Z dash is not fixed on the body, it is parallel to the original system, now I have got a body system which is you can say small, well let me call it small o here, small x, small y, this is my body fix system. So, body fix system is the colour will help, a system like that, this is my small x, this is my small z and small y will come, may be I will just draw this two in a next one in a bigger way that will be easier.