480 = 3,000 x R x 2. What is R?

The graph represents the gallons of water in a water tank with respect to the number of hours since it was completely filled

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.

Select the correct answer and solve for y