The cost of a can of iced-tea mix at SaveMore Grocery is $4.75. The
function f(x)=4.75x gives the cost
of x cans of iced-tea mix. Graph this
function and give its domain and
range.

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.