In a random sample of 400 cars of a particular model, 5 have a malfunctioning defect. at this rate, how many of 10,000 cars will have a malfunctioning defect? label your answer and show your work.

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.