Atext font fits 12 characters per inch. using the same font, how many characters can be expected per yard of text?

36 characters
144 characters
360 characters
432 characters

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.