Problems for September 23, from the exam problem collection except the "*" marked. 
EDIT: 111 out, 109 in.


* Suppose Y = Y (t) is national product, C(t) is consumption at time t, and I is investment,
which is constant. Suppose Y' = k (C + I ? Y) and C = aY + b, where a, b, and k are constants
with 0 < a < 1. 
Derive a differential equation for Y . Find its solution with Y (0) = z is given.


43


100


109


* The price vector is (2, 3, 5) and you can just afford the commodity vector (10, 5, 8). 
What is your budget constraint?


45 (requires material to be presented in Tuesday's lecture)