In 1942, school children brought their dimes and quarters to school each week. which of the following items would the children buy that would eventually add up to the price of a war bond?
a. war stickers

b. defense stamps

c. patriot pins

d. yellow ribbon

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.