Sahil got 28 questions right on the math test. Angelina got 7 more wrong answers than Sahil. There where 40 questions on the test. How many answers did Angelina get right on the math test?

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.