On August 31, the end of the first year of operations, during which 18,000 units were manufactured and 13, 500 units were sold, Fairfield Inc. prepared the following income statement based on the variable costing concept: A. Determine the unit cost of goods manufactured, based on (a) the variable costing concept and (b) the absorption costing concept. B. From a product costing perspective, what is the basic difference between absorption costing and variable costing? Which method is better suited for external users and why? C. Fairfield is operating at 85% capacity and is considering a proposal to increase current production by 25%. Which costing method, absorption or variable costing; should be used to evaluate the proposal and why? D. If the proposal would increase current production by 10%, would your answer be different? Why