The telephone company offers two types of service. with plan a, you can
make an unlimited number of local calls per month for $18.50. with
plan b, you pay $6.50 monthly, plus 10 cents for each min of calls after
the first 40 min. at least how many min would you have to use the tele-
phone each month to make plan a the better option?

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.