Under the marginal costing approach adopted by Eko Plastics Limited, which of the following costs would be included in the cost of a unit of inventory for internal management reporting purposes?

Under marginal costing, only variable production costs are included in unit inventory cost. Direct materials are a prime variable cost that varies directly with output. Fixed costs such as factory rent, building depreciation, and the supervisor's fixed salary are period costs written off in the period incurred and are not carried forward in inventory valuation.