(a) The following figure shows one graphical illustration of STL format representation of the quadrilateral shape ABCD. Use graphical illustration to show an alternative STL format representation of the same quadrilateral shape ABCD if any. (5 marks) A B D C A (b) Write the text file of the alternative STL format representation in (a). (5 marks) (c) Explain why STL file is incapable of representing certain properties of a 3D model Give an example of existing alternatives to STL file format. (10 marks) (d) An STL file is sliced into layers for additive manufacturing. Give an example of how to represent contours on a layer