the isosceles triangle has a base that measures 14 units. the value of y, the length of each leg, must be . equal to 7., between 7 and 14., greater than 7., between 14 and 28

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.