The Speed of a Satellite in a Circular Orbit of Radius

Multiple Choice

The speed of a satellite in a circular orbit of radius $R$ around the earth is $3.0 \mathrm{~km} / \mathrm{s}$ . The speed of another satellite in a different circular orbit around the earth is one-half this value. What is the radius of that satellite's orbit?

A) $4 R$
B) $2 R$
C) $\sqrt{2} R$
D) $R / \sqrt{2}$
E) $R / 2$
F) $R / 4$
G) Some other multiple of $R$ (specify)