Final answer:
The total cost to be accounted for in the department's cost reconciliation report for March would be $340,000, calculated by summing the beginning inventory of $40,000 and the costs added during the month of $300,000.
Step-by-step explanation:
The total cost to be accounted for in A Corporation's processing department for March would be the sum of the beginning work in process inventory and the costs added during the month. Therefore, we calculate this as:
Beginning work in process inventory + Costs added to production = Total cost to be accounted for
$40,000 + $300,000 = $340,000
This figure represents the total costs that the department needs to account for within the given month.