題組內容

V.A father-son pair use the following income streams to finance their living in 2021 and 2022. The father earns $100 in 2021, but plans to retire early and so will only earn $20 in 2022. The son is undergoing a training program and earns only $20 in 2021, but will finish the training and earn $100 in 2022. By consuming $c1$ in 2021 and $c2$ in 2022, the father obtains utility $UF = \min\{c1, c2\}$, and the son obtains $US = \ln c1 + 0.8 \ln c2$. Both $c1$ and $c2$ are continuous.


(a)(4%) Suppose that they can save or borrow at zero interest rate, which is close to current situation. How much, if any, would the father and son, respectively, optimally save or borrow in 2021?