  From equation (11a) it follows that \(F_K = \mu\), which means the rate of return on investment is constant. From equation (11b) it follows that \(\sigma\) is the elasticity of marginal well-being. Notice also that \(U(C) \rightarrow -\infty\) as \(C \rightarrow 0\) and that, under the chosen normaliztion of the \(U\)-function, \(U(C) \rightarrow 0\) as \(C \rightarrow \infty\). Using equation (11a) in equation (1) yields,