PROBLEM If the size of a new Kuiper object is 0.0150 arc sec in angular size as seen from a distance of 42.00 AU, what is the true diameter? If it has a satellite with a period of 5.50 hours at a semimajor axis of 12500.0 km, what is the mass? What is the resulting density? What do you it is composed of? What I know: I know that I use V=4/3(pi)r^3 to get the density and previous equations to solve for mass. I don't know how I am supposed to apply the 0.0150 arc seconds or distance to solve for the diameter. What is the equation for that?