Tara and Sima are purchasing t-shirts and sweaters in the same store for their upcoming trip. Tara bought 4 t-shirts and 2 sweaters and paid $114.32. Sima purchased 3 t-shirts and 1 sweater, which cost $72.15. Find the cost for a t-shirt and a sweater. Type your equations and end result.

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.