Galileo is often credited with the early discovery of four of Jupiter's many moons. The moons orbiting Jupiter follow the same laws of motion as the planets orbiting the Sun. One of the moons is called Io - its distance from Jupiter's center is 4.2 units and it orbits Jupiter in 1.8 days. Another moon is called Ganymede; it is 10.7 units from Jupiter's center. Make a prediction of the orbital period of Ganymede using Kepler's laws.