4. Consider a small open economy with desired national saving of Sd = 30 + 200rw and desired investment of I d = 30 - 200rw.

Calculate national saving, investment, and the current account balance in equilibrium when the real world interest rate is

a. rw = 0.025.

b. rw = 0.05.

c. rw = 0.0.

d. Now suppose something causes desired national saving to increase by 10, so that it is now Sd = 30 + 200rw. Repeat parts (a), (b), and (c).

e. Suppose, with desired national saving at its original level of Sd = 20 + 200rw, something causes desired investment to rise by 10, to I d = 40 - 200rw.

Repeat parts (a), (b), and (c).