A sphere has a diameter of 24 units. What is it’s volume in cubic units? A: 576 B: 1728 C: 2304 D: 6912

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.

Pls the last one and it has to be like number 6

If x varies directly as y, and x = 7.5 when y = 10, find x when y = 4