Alexandra has a home-based business putting on children’s parties. she charges $60 to design the party and then $4.00 per child. write a function rule that relates the total cost of the party to the number of children n.

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.