A Cartesian Puzzle


The eight sets of coordinates below define various quadrilaterals (four-sided shapes). In each case one coordinate is missing.
  1. $(2,11), \; (0,9),\; (2,7),\; (?,?)$
  2. $(3,7),\; (3,4),\; (8,4),\; (?,?)$
  3. $(18,3),\; (16,5), \;(12,5),\; (?,?)$
  4. $(13,12),\; (15,14),\; (12,17),\; (?,?)$
  5. $(7,14),\; (6,11),\; (7,8),\; (?,?)$
  6. $(15,9),\; (19,9),\; (16,11),\; (?,?)$
  7. $(11,3),\; (15,2),\; (16,6),\; (?,?)$
  8. $(9,16),\; (2,9),\; (9,2),\; (?,?)$

These eight quadrilaterals are all symmetrical. This may be rotational or line symmetry or both. The shapes are all in the first quadrant.

The set of eight missing coordinates define another shape - this time with eight sides which has both rotational and line symmetry.

Can you draw this new eight-sided shape on a graph like the one below?

Grid.