Please help!

Which expression do you get when you eliminate the negative exponents of 4a^2 b^216a^-3 b

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.

What rotation was applied to triangle def to create d’e’f’?