Find the average energy generation rate per unit mass of the core of the Sun if the mean core density is 3.16 x 10^4 kg/m^3, the density at the surface of the core at 0.25 solar radius is 2.45 x 10^⁴ kg m^-3, the mass of the core is 6.96 x 10^29 kg and the luminosity of the Sun is 3.83 x 10^²⁶ Joules/sec?