A. This answer does not include the variable factory overhead as an inventoriable cost.

B. This answer includes the variable selling costs as an inventoried cost. Selling costs, whether variable or fixed, are not inventoried under either variable costing or absorption costing, because they are not production costs.

C. This answer includes fixed factory overhead. Though it is a production cost, the variable costing method includes only variable costs of production in inventory.

D. Under the variable costing method, only the variable costs of production are inventoriable costs. Therefore, the costs that are inventoriable are: direct materials ($300,000), direct labor ($100,000) and variable factory overhead ($50,000). This is a total of $450,000.