I gotta find an answer or a push to the right tracks on this question. Suppose a spacecraft is in a circular orbit about a distant planet. the spacecraft emits a continuous radio signal with a wavelength of 6m. The signal's wavelength varies between 5.99969m and 6.00031m; the period of variation (full period of wavelength) is 5 hours. What is the mass of the planet? Assume that you are located in plane of the spacecraft's orbit and knowing that circumference is 2piea (a = radius) and that speed = distance / time. Thanks in advance!