3. Let's extend our growth model to include land, which is an important factor of production of many countries. The model is as follows, Kt+1 = (15)K+It Y, = F(K,,N,L) I, = S; F(K,,N,L) = Kf'NL\" St = 5?} where L denotes the amount of land in the economy (which is xed) and or, ,6, 7 > 0. (a) Suppose or + ,8 = 1. Does the production function F exhibit constant returns to scale? Explain. (b) Assume from now on a + ,6