Targeted 10 A fruit stand is selling watermelons for $5, cantalopes for $3, pomegranates
for $2, and grapefruits for $2. Julie dropped by the fruit stand and bought r
watermelons, n cantalopes, r pomegranates, and n grapefruits. How much
did Julie spend at the fruit stand?

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.