Heedy Company is trying to decide how many units of merchandise to order each month. The company policy is to have 20% of the next months sales in inventory at the end of each month. Projected sales for August, September, and October are 30,000 units, 20,000 units, and 40,000 units, respectively. How many units must be purchased in September? a. 24,000 b. 18,000 c. 28,000 d. 22,000