$3.$ Two identical planets, P$1$ and P$2,$ orbit a star in concentric circular orbits in the star's equatorial plane.

P$1$ has an orbit of radius a$1$ and period T$1$; and P$2$ has an orbit of radius a$2$ and period T$2.$ Given that

$($a$2/$a$1)=1/8,$ what is the ratio of the periods $($T$2/$T$1)?$

A$)0\mathrm{.}10$

B$)0\mathrm{.}098$

C$)0\mathrm{.}044$

D$)0\mathrm{.}032$

E$)8$