Callisto and Io Are Two of Jupiter's Satellites

Multiple Choice

Callisto and Io are two of Jupiter's satellites. The distance from Callisto to the center of Jupiter is approximately 4.5 times farther than the distance from Io to the center of Jupiter. How does Callisto's orbital period, T_C, compare to that of Io, T_I?

A) T_C = 4.5 T_I
B) T_C = 21 T_I
C) T_C = 9.5 T_I
D) T_C = 0.2 T_I
E) T_C = 2.7 T_I