Free points and brainiest if you get this right

What is the measure of ac? 5 units 13 units 26 units 39 units

What is the 17th term in the arithmetic sequence in which a6 is 101 and a9 is 83

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.