a. a recent stock market boom has increased household wealth by $20 billion, which initially increases consumption by $9 billion, and the marginal propensity to consume in the economy is equal to 0.8. after the multiplier effect, aggregate spending (ad) will (click to select) by $ billion. b. rising interest rates reduce domestic consumption by $6 billion and reduce investment by $5 billion, thereby initially reducing overall spending by $11 billion. the marginal propensity to consume in the economy is equal to 0.8. after the multiplier effect, aggregate spending (ad) will (click to select) by $ billion.