John spent 2/3 of his money on a pen and calculator .the calculator cost 3 times as much as the pen .if the calculator cost $24,how much money did he have left

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.