3) A tailor, when asked to stitch dresses for a school's annual programme, says he would stitch 25 dresses a day and finish the work in 20 days. If the school requests him to
finish and deliver the dresses 5 days earlier, at least how many extra dresses would he
need to stitch every day?

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.