Carson is going on a work trip. He will get reimbursed for his expenses for driving his own car. He will get a flat rate of 30,
plus $1.25 per mile (m) he drives. Write the equation
representing the total reimbursement (R) he should expect to
see in his bank account when he comes back.

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.