1. The problem statement, all variables and given/known data The density of a certain planet varies with radial distance as: ρ (r)= ρo(1- αr/Ro) where Ro= 3.98 x 106 m is the radius of the planet, ρo= 4980 kg/m3 is its central density, and α = 0.17. What is the total mass of this planet ? Calculate the weight of a one kilogram mass located on the surface of this planet. 2. Relevant equations ρ = m/v 3. The attempt at a solution since ρ= m/v then m = ρv v of a planet = 4/3∏ R^3 so i substitute the given info on the equations and got m = ρo(1- αr/Ro) * 4/3∏ R^3 calculate all of those and I realize that i don't know what r is. so I assume that r = Ro but I got the wrong answer any help?