Arestaurant ordered $900 worth of plates, some of which cost$5 each and some of which cost $10 each. if twice as many $10 plates as $5 plates were ordered, what was the total number of plates ordered
(options)
.86
.96
.102
.105
.108

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.