Final answer:
Parsons Corporation must produce 18,500 units during the month.
Step-by-step explanation:
To find the number of units that must be produced during the month, we need to calculate the net production needed.
Net production = Units to be sold + Desired ending inventory - Beginning inventory
Net production = 18,000 + 6,000 - 5,500 = 18,500 units
Therefore, Parsons Corporation must produce 18,500 units during the month.