A newly discovered planet $X$ , has twice the mass of Earth. Planet $X$ is orbited by a moon, which has twice the mass of Earth's moon. The orbital radius of the moon orbiting Planet $X$ is the same as the orbital radius of Earth's moon. How does the orbital speed of the moon orbiting Planet $X$ compare to the orbital speed of Earth's moon?
(A) It orbits at the same speed as Earth's moon.
(B) It orbits at $\frac{1}{2}$ the speed of Earth's moon.
(C) It orbits at 2 times the speed of Earth's moon.
(D) It orbits at $\sqrt{2}$ the speed of Earth's moon.
(E) It orbits at $\frac{\sqrt{2}}{2}$ the speed of Earth's moon.