Let the economy of a country named, Happy Land be in a long-run equilibrium position. Using a diagram, explain how each of the following affects equilibrium real GDP and price level in the short-run, as well as in the long-run:

A) An increase in income tax rate

B) An decrease in exchange rate

C) A significant increase in foreign income caused by an economic boom in the rest of the world

D) A decrease in nominal money supply