The density of a certain planet varies with radial distance as: ρ(r)= ρ0(1- αr/R0). R0=4.4668*10^5 m is the radius of the planet. p0= 5140 kg/m^3 is its central density, and aplha=0.180. a) Calculate the total mass of this planet. b) Calculate the weight of a one kilogram mass located on the surface of that planet.