a star has its total mass given by the expression: 3 where pe is a constant equal to the density at the center of the star and r is the radius at the surface of the star. the density of the star depends linearly on radius as follows: a(r) = ar + b where a and b are constants. a. determine the complete expression for ρ(r) by finding a and b. you may assume spherical symmetry b. assuming the star is in hydrostatic equilibrium, find an expression for the internal pressure as a function of radius, p(r). c. find and expression for the gravitational potential energy of this star, ω, as well as its total internal energy, u.