Please help me sort out these problems I'm stuck on in my test review.

The __________ effect is the tendency of a given change in exogenous planned expenditure to cause a greater change in equilibrium GDP.

a. twin deficit

b. unplanned investment

c. multiplier

d. Keynes

If there is an exogenous $1 billion increase in exports, beginning from a state of equilibrium, what would be the expected?

a. A decrease in equilibrium GDP

b. An increase of less than $1 billion in equilibrium GDP

c. An increase of more than $1 billion in equilibrium GDP

d. No change in equilibrium GDP

For the economy to be considered to be in equilibrium, imports ______ equal exports and investment ______ equal saving.

a. must; must

b. must; need not

c. need not; need not

d. need not; must