The minute hand on a watch is 8mm long and the hour hand is 4mm long. how fast is the distance between the tips of the hands changing at one o'clock? round your answer to the nearest tenth.

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.