Final answer:
The method being used when all fixed and variable manufacturing costs are included as inventoriable costs is absorption costing.
Step-by-step explanation:
The method being used when all fixed manufacturing costs and variable manufacturing costs are included as inventoriable costs is absorption costing.
Absorption costing is a method of accounting where all manufacturing costs, both fixed and variable, are allocated to the cost of a product and become part of the inventory until the product is sold.
For example, if a company incurs $100 of fixed manufacturing costs and $200 of variable manufacturing costs for producing a product, the total cost of the product under absorption costing would be $300. This $300 is then assigned to the inventory and is included as part of the cost of goods sold when the inventory is sold.