Apackage of dental floss contains 25 m of floss. how many yards of floss are in the package? if a dental hygienist uses about 18 in. of floss for each patient, how many patients can be cleaned with one package of floss?

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.