Rotating a GUi Texture based on Touch

So I’m trying to create a steering wheel type effect for my Android game using this image(http://i.cubeupload.com/GaM1z2.jpg). What I want to do is that whenever the user touches the GUI Texture, the image will rotate so that the small circle will change to where the user has touched. I don’t want the position to change, just the rotation angle. How would I go about achieving this?

Thanks

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