The ratio of the volumes of two right circular cylinders A and B is $\frac{x}{y}$ and the ratio of their heights is a : b. What is the ratio of the radii of A and B?

$\frac{yb}{xa}$ $\sqrt{\frac{xa}{yb}}$ $\frac{xb}{ya}$ $\sqrt{\frac{xb}{ya}}$

$\sqrt{\frac{xb}{ya}}$