Answer:
a. Increased real GDP by $20,000.
Explanation:
Changes in real GDP are calculated by multiplying changes in total output times the base year's price. Assuming that last year was our base year, the price of pizzas is $10 each. The change in real GDP is given by the larger amount of pizzas sold:
change in real GDP = (12,000 - 10,000) x $10 = 2,000 x $10 = $20,000