If a 12-sided regular polygon rotates about its center, at which angle of rotation will the image of the polygon coincide with the preimage?

75°

45°

36°

30°

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.