After the Sun exhausts its nuclear fuel, its ultimate fate may be to collapse to a white dwarf state. In this state, it would have approximately the same mass as it has now, but its radius would be equal to the radius of the Earth.

Question

After the Sun exhausts its nuclear fuel, its ultimate fate may be to collapse to a white dwarf state. In this state, it would have approximately the same mass as it has now, but its radius would be equal to the radius of the Earth.
(a) Calculate the average density of the white dwarf. 
  kg/m3

(b) Calculate the surface free-fall acceleration. 
  m/s2

(c) Calculate the gravitational potential energy associated with a 4.62-kg object at the surface of the white dwarf. 
  J