Answer:
Step-by-step explanation:
volume of a cone is
V = ⅓πr²h
V = ⅓π(x/2)²x = ⅟₁₂πx³
Use the geometric mean for right triangles here. Like this

. Cross multiply to get

, and

. That simplifies down to

. Pull out the 9 as a perfect square of 3 and you're left with

, first choice above.
You can see that there are 6 rock CDs, over a total of

So, the ratio of rock CDs over the total number of CDs is

Which is 15%.
So, yes, the answer is A
4 united states customary cups