A weird new planet has been discovered on the outskirts of our solar system. The planet has the same mass as Venus but no one has determined its radius as yet and it has a gigantic moon, fully 1/3rd the mass of the planet itself. The moon is in an elliptical orbit with a semi-major axis of 20,000[km] and an eccentricity of 0.4. How long, in days, does it take the moon to complete one orbit around the planet? BIG HINT:That's a really big moon.

Please show us your attempt at solving this, then we can comment. Hint: the value for - the gravitational parameter for this problem - includes the masses of both the planet and its moon.