The Equilibrium Level of GDP will Change in Response to Changes in the Investment Schedule

No. 1
Statement : The equilibrium level of GDP will change in response to changes in the investment schedule

The Answer is TRUE
Since GDP equals the national income of a country that is affected by the investment factor.
Y = C + I + G + ( X – M), where :
Y : Yield (Pendapatan)
C : Consumption (Konsumsi)
I : Investment (Investasi)
G : Government Spending (Pengeluaran pemerintah)
X : Export (Ekspor)
M : Import (Impor)

Investment

Each firm has a list of investment projects that can be rank ordered by expected rate of return as profit (π) then compared with the opportunity cost of money, i.e., the interest rate (r). This schedule was introduced by Keynes and is known as the 'marginal efficiency of capital schedule'. While mainstream economists have assumed rationality in calculating the schedule, Keynes stressed limitations of long-run expectations due to true ignorance, i.e., lack of knowledge about the future. (see: The General Theory of Employment, Interest and Money These limitations combined with his contrast between 'enterprise' (investing for the long-run) and 'speculation' (playing the market) are directly applicable to the Crash of 2008.
Keynes’s whole theory of unemployment is ultimately the simple statement that rational expectation being unattainable, we substitute for it first one and then another kind of irrational expectation: and the shift from one arbitrary basis to another gives us from time to time a moment of truth, when our artificial confidence is for the time being dissolved, and we, as business men are afraid to invest, and so fail to provide enough demand to match our society’s desire to produce. Keynes in the General Theory attempted a rational theory of a field of conduct which by the nature of its terms could be only semi-rational. But sober economists gravely upholding a faith in the calculability of human affairs could not bring themselves to acknowledge that this could be his purpose.
Shackle, G.L.S., The Years of High Theory: Invention and Tradition in Economic Thought 1926-1939,
Chapter 11 - To the 'QJE' from Chapter 12 of the "General Theory': Keynes's Ultimate Meaning,
Cambridge at the University Press, 1967
.

Investment, in economic theory, means the acquisition of the means of production (including goods for selling) with money capital. The decision to invest (or level of investment) depends on expected real profit rate and the real interest rate.
Expected real profit rate equals the monetary profit rate minus the inflation rate. All things being equal, the higher the real profit rate the higher the level of investment.
Real interest rate equals the monetary interest rate minus the inflation rate. All thing being equal, the higher real interest rate the lower investment. The interest rate is, in effect, the price of money. Because investment involves the acquisition of the means of production using money capital, if the real interest goes up, the opportunity cost of investment goes up, that is the purchase of interest earning assets rather than means of production becomes more attractive.
Changes in expected real profits and real interest rates will affect the level of investment. Changes in real GDP will not. In this sense, investment is autonomous of real GDP. Its formula is: I = (π, r), i.e., some function of the expected rate of return or profit (π) and the interest rate (r).

Government Expenditure
Government spending is funded out of taxes on the income earned by households and/or borrowing on financial markets. It is determined politically, that is government spending influences real GDP but real GDP does not necessarily influence government spending. In this sense, government expenditure is autonomous of real GDP. Its formula is G = (politics), i.e., government spending is a political not a strictly economic decision.

Reference : http://www.cliffsnotes.com/WileyCDA/CliffsReviewTopic/The-Keynesian-Theory.topicArticleId-9789,articleId-9742.html#ixzz0XI4bdvQW
http://www.compilerpress.ca/ElementalEconomics/mac_2_1.htm

The Keynesian Theory

Keynes's theory of the determination of equilibrium real GDP, employment, and prices focuses on the relationship between aggregate income and expenditure. Keynes used his income-expenditure model to argue that the economy's equilibrium level of output or real GDP may not corresPond to the natural level of real GDP. In the income-expenditure model, the equilibrium level of real GDP is the level of real GDP that is consistent with the current level of aggregate expenditure. If the current level of aggregate expenditure is not sufficient to purchase all of the real GDP supplied, output will be cut back until the level of real GDP is equal to the level of aggregate expenditure. Hence, if the current level of aggregate expenditure is not sufficient to purchase the natural level of real GDP, then the equilibrium level of real GDP will lie somewhere below the natural level.