Here's the problem: Phobos and Deimos 2 satalites of mars, ahve orbits with average radii of 9380km and 23500km respectivly. The period of Phobos is .319 earth days. Whats is the period of Demos? I ahve it set up like this: Rp=9380 RD=23500 Pp=.319 Pd=? and i know (Ta\Tb)sq'ed =(Ra\Rb)cubed. Am I right in doing this? How do I choose who is A and who is B?