Answer
0.378
Work Step by Step
The speed for an object orbiting a distance $r$ around a mass $M$ is given by $v=\sqrt{\frac{GM}{r}}$ as found in Example 5-12.
$$\frac{v_A}{v_B}=\frac{\sqrt{\frac{GM_{star}}{r_A}}}{\sqrt{\frac{GM_{star}}{r_B}}}=\sqrt{\frac{r_B}{r_A}}=\sqrt{\frac{1}{7.0}}=0.378$$