Final answer:
To find the required production units, subtract the expected unit sales from the total required units, which results in 6,000 units required for production. Option a is correct.
Step-by-step explanation:
The expected unit sales are given as 48,000 units, and the total required units are 54,000 units. To determine the required production units, the expected sales are subtracted from the total required units: 54,000 units (total required) - 48,000 units (expected sales) = 6,000 units. Therefore, the required production units that the company must manufacture in addition to expected sales to meet the total required units are 6,000.