Given this information, what can we determine about this planet

This was on a previous exam of mine and I got it wrong. I decided to redo the exam today but I'm still not getting the right answer...

Imagine there is a planet orbiting another star at 2 AU, with a 1-year orbiting period. The planet has a moon orbiting the planet at the same distance as Earth's moon, however it takes 2 months. What can we assume about this planet?
- Massive than Earth
- Less massive than Earth
- Same mass as Earth

I thought it was less massive than Earth, but it's not right--the correct answer is the first one, that it's more massive. How would you approach this problem?

If the moon is at the same distance as earth's moon, but orbits slower, then of course the planet's mass must be less. If it was more, the moon would orbit faster. By the way, the orbital period of the planet and its distance from the star seem to be irrelevant in this problem.

The distance from the star certainly makes a difference. For the planet to make a 1 year orbit at twice the distance, right off tells you more mass. So with the higher mass probably means larger size which would explain the longer orbit of moon.

well the gravitational pull how have to slower and maybe the planet would be smaller to but then again i'm in 7th grade so... :l good luck on ur next exam

I assume your first answer is supposed to be "MORE Massive than Earth"

Newton's formula for calculating orbital periods is the guiding physics here.

The orbit of the planet around its star is not significant to the question.

The below paragraphs comes from the source article in wikipedia

"Scaling"

The gravitational constant G has been calculated as:

(6.6742 ± 0.001) × 10−11 (kg/m3)−1s−2.

Thus the constant has dimension density−1 time−2. This corresponds to the following properties.