申論題

2. (15%) One of the debt models proposed by Evsey Domar, a Keynesian economist, can be described as follows. Let D and I respectively denote the national debt and national income, and assume that both are functions of time t. Furthermore, both the time rates of change of D and I are assumed to be proportional to I, so that

Supposc /(0) = I₀ and D(0) = D₀.