"Low demand in this year's economy caught producers unaware, forcing their inventories to increase." How does this inventory change appear in the GDP calculation when adding up all expenditures? a) it is added when measuring GDP, as an element of investment demand b) it is added when measuring GDP, as an element of consumption demand c) it is subtracted when measuring GDP, as an element of investment demand d) it is subtracted when measuring GDP, as an element of consumption demand