(a) Show that in the model in Section 18.3.2, if population grows at some constant rate n > 0 in each country, there does not exist a steady-state equilibrium.
(b) Construct a variation of this model along the lines of the semi-endogenous growth models of Section 13.3 in Chapter 13, where the strong scale effect is removed and there is long-run growth at a constant rate (when population grows at the rate n > 0 in each country).
(c) Provide a full characterization of the steady-state world equilibrium in the case described in part b.