Refer to the information provided in Table 8.9 below to answer the questions that follow. Table 8.9 All Figures in Billions of Dollars Aggregate Output Aggregate Consumption Planned Investment 100 160 20 200 240 20 300 320 20 400 400 500 480 20 20 Refer to Table 8.9. At an aggregate output level of $100 billion, the unplanned inventory change is Select one: a. -$30 billion. O b. -$20 billion O c $120 billion. d. -$80 billion