Assume That You Discovered a New Planet in the Solar

Assume that you discovered a new planet in the Solar System. To study it, you measured the orbital period and semimajor axis of one of its moons and deduced that the planet's mass was 4 * 10²⁵ kg (7 M_Earth) , then you observed the planet occult a background star and deduced that its radius is 12,000 km (2 R_Earth) . What is this planet's average density? Is this planet's chemical composition more similar to a rocky terrestrial planet or a giant planet? For comparison, the density of iron, rock, and water are approximately 9,000 kg/m³, 3,000 kg/m³, and 1,000 kg/m³, respectively.

A) The planet's average density is 1,200 kg/m³, and its composition is similar to that of giant planets.
B) The planet's average density is 1,200 kg/m³, and its composition is similar to that of terrestrial planets.
C) The planet's average density is 3,100 kg/m³, and its composition is similar to that of terrestrial planets.
D) The planet's average density is 5,500 kg/m³, and its composition is similar to that of giant planets.
E) The planet's average density is 5,500 kg/m³, and its composition is similar to that of terrestrial planets.