Picking digits from the list 1, 2, 3, 4, 5, 6, 7, 8, 9 just once, we build two four-digit natural numbers in such a way that their sum is as small as possible. what is the value of this smallest possible sum?

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.