Abus averages 60 mi/h traveling to its destination in the first half of its trip through an expressway and 72 mi/h in the second half traveling through a motorway. what is the bus's average speed for the entire trip rounded to the nearest tenth?
a) 64.2 mi/h
b) 63.0 mi/h
c) 65.5 mi/h
d) 66.0 mi/h

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.