The angular separation between the barycentre (i.e., the centre of mass) of the Pluto-Charon system and Charon itself is 0.7405". a) [2] Calculate the semi-major axis of both Charon's and Pluto's orbits around the barycentre, in km. [Hint: you'll need to use the distance information from question 1.] b) [3] Using your answers to question 1(b), determine the individual masses of Pluto and Charon, in kg. If you didn't get a reliable answer for 1(b), use 1.60 x 1022 kg.

I don't understand the formulas and need step-by-step breakdown of how to get to answer.