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. [asy]import graph;
size(50);
for(int i = 0; i<5; ++i)
for(int j = 0; j<5; ++j)
fill(Circle((i,j),.1));
[/asy]
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
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. [asy]import graph;
size(50);
for(int i = 0; i<5; ++i)
for(int j = 0; j<5; ++j)
fill(Circle((i,j),.1));
[/asy]
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
\frac{2}{5}
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. [asy]import graph;
size(50);
for(int i = 0; i<5; ++i)
for(int j = 0; j<5; ++j)
fill(Circle((i,j),.1));
[/asy]
train