my problem involves creating a graph of log10(a) vs log10(P) of the Galilean satellites and 3 others, then calculate the mass of jupiter from the graph. P= period of the satelite, a is the semi-major axis I have created the graph and it seems to be right since the of the trend line is 3/2. My problem is that I am unsure how to go about calculating the mass from the graph. to get the equation y = 1.5012x - 8.1973 I have tried using m1+m2= (4*P^2*a^3)/(G*P^2)G being the universal gravitational constant 6.67206 x 10-11 m3/kg s2. I used P and A values of Io. Unfortunatly that produced a rather large value and doesn't utilize the graph at all. Any help or nudges in the right direction would be greatly appreciated, Thanks!