The unplanned inventory investment should be $900 at the time when the scenario should be seen.
Calculation of the unplanned inventory investment
Since
GDP = $8,000
Autonomous consumption = $500
Investment spending = $200
Marginal propensity = 0.8
So, we can calculate the unplanned inventory investment by using following formula:
GDP = ( autonomous consumption + investment spending) + (marginal propensity × GDP) + Unplanned inventory investment
So, $8,000 = $700 + (0.8 × $8,000) + Unplanned inventory investment
$8,000 = $700 + $6,400 + Unplanned inventory investment
$8,000 = $7,100 + Unplanned inventory investment
So, Unplanned inventory investment = $8,000 - $7,100
= $900
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