Please help I don't understand

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.

Hello, i need compare km^2 and km. what's difference in this?

Luis has a cooler filled with cans of soda.for every 5 cans of coke there are 3 cans of sprite.if there are 25 cans of coke, how mant cans of sprite are there?