1. The problem statement, all variables and given/known data The question is attached 2. Relevant equations Kepler's laws and gravitational equations 3. The attempt at a solution the question gave me a and T, I related it with Kepler's third law a^3/T^2, then I don't know what to do next. The answer of part a is 1.27 x10^17 /r^2 , part b = 1.9 x 10^27, How can I find GMm as the question only provided a and T?