Final answer:
The ROI of the parking garage is 20%.
Step-by-step explanation:
The Return on Investment (ROI) of the parking garage can be calculated by dividing the net profit by the cost of the investment. The net profit is the additional sales generated minus the cost of the investment. In this case, the net profit is $600,000 - $500,000 = $100,000. Therefore, the ROI is $100,000 / $500,000 = 0.2, or 20%.