I may be wrong, but I think you're trying to say that Planet-A is
<em>3 times as far from the sun</em> as Planet-C is.
If that's the real question, then the answer is that the period of Orbit-A
is about<em> 5.2</em> times as long as the period of Orbit-C .
Orbital period ≈ (proportional to) (the orbital distance) ^ 3/2 power.
This was empirically demonstrated about 350 years ago by Johannes
and his brilliant Kepple, and derived about 100 years later by Newton
from his formula for the forces of gravity.
The centripetal force acting on the space shuttle as it orbits Earth is equal to the shuttles momentum
