The Hipparcos Satellite Was Able to Measure Parallax for Stars

Multiple Choice

The Hipparcos satellite was able to measure parallax for stars out to about 150 pc.This distance includes roughly 2.5 million stars.The new Gaia satellite should be able to measure the parallax of roughly a billion stars.Assuming the density of stars is approximately constant,what distance would this correspond to? (Hint: the volume of a sphere is proportional to the cube of the radius.)

A) 35 pc
B) 167 pc
C) 350 pc
D) 20 kpc