$P_1= \large\frac{4T}{r_1}$
$P_2= \large\frac{4T}{r_2}$
$\large\frac{P_1}{P_2}=\frac{r_2}{r_1}$
$\large\frac{r_2}{r_1}$$=3$
$r_2=3r_1$
ratio of volumes
$\large\frac{V_1}{V_2}=\frac{\Large\frac{4 \pi}{3} r_1^3}{\Large\frac{4 \pi}{3}r_2^3}$
$\qquad= \bigg(\large\frac{r_1}{r_2}\bigg)^3$
$\qquad=\bigg(\large\frac{1}{3}\bigg)^3$
$\qquad= \large\frac{1}{27}$
Hence b is the correct answer.