Jack's overtime wage is $3 per hour more than his regular hourly wage. he worked for 5 hours at his regular wage and 4 hours at the overtime wage. he earned $66. find his regular wage.

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.