Suppose that the marginal propensity to consume is 0.8, and investment spending increases by $100 billion. The increase in aggregate demand/expenditure is: 1) $100 billion, the same amount as investment spending. O 2) $125 billion, composed of $100 billion in investment spending and $25 billion in consumption. 3) $80 billion, composed of $100 billion in investment spending and a decrease in consumption of $20 billion. 4) $500 billion, composed of $100 billion in investment spending and $400 billion in consumption