At 10 a. m., there were 12 people in a swimming pool. at 11 a. m., there were 27 people in the pool. what was the percent of increase in the number of people in the swimming pool from 10 a. m. to 11 a. m.?

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.