The density of a certain material is such that it weighs 2 grams per milliliter of volume. Express this density in kilograms per pint. Round your answer to the nearest hundredth.

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.