Bean seeds from supplier A have 85% germination rate and those from supplier B have 75% germination rate. A seed-packing company purchases 40% of its seed from A, 60% from B, and mix them together. Find the probability that a seed selected at random from the mixed will germinate.

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.