A circular window is drawn on architectural plans where each unit is a foot on a coordinate grid. The window is modeled by the equation (x - 4)² + (y - 12)² = 9. The equation indicates that the center of the window is 4, 6, 9, 12
feet from the ground and the distance the window spans is 3, 4, 6, 12
feet.

Right answers only just comment if you don't understand

Set $r$ is a set of rectangles such that (1) only the grid points shown here are used as vertices, (2) all sides are vertical or horizontal and (3) no two rectangles in the set are congruent. if $r$ contains the maximum possible number of rectangles given these conditions, what fraction of the rectangles in set $r$ are squares? express your answer as a common fraction.