Assume that in a small economy where full employment always prevails, national saving is 300. Domestic investment is given by I = 400 - 20r, where r is the real interest rate in percent.

(a) What would the equilibrium interest rate be if the economy were closed? Type only the numeric value in the box.

(b) If the economy is open and the world interest rate is 10 percent, what will investment be?

(c) What will the trade deficit or surplus be?