Which of the following is not something that money does in an economy?
a.
measure the value of commodities
b.
store the value of commodities
c.
keep the rate of inflation low
d.
allow producers and consumers to trade commodities

select the best answer from the choices provided

a
b
c
d

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.