Eula needs to buy binders that cost $4 each and notebooks that cost $2 each. She has $20. The graph
of the inequality 4x + 2y s 20, which represents the
situation, is shown.
What is the greatest number of binders Eula can buy?
What is the greatest number of notebooks Eula can
buy?
If Eula buys 7 notebooks, what is the greatest number
of binders she can buy?

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.