Suppose that a country with a closed economy has private saving of $5 trillion and a government

Question:

Suppose that a country with a closed economy has private saving of $5 trillion and a government budget deficit of $3 trillion.
a. What is the equilibrium level of investment?
b. If the economy is open and has net capital inflow of $6 trillion, what is the level of investment?
c. Explain how an open economy can allow a country to run a budget deficit and still have a high level of investment.