Determine which costing method​ (variable costing or absorption​ costing) accounts for fixed manufacturing costs as costs of the​ period: a. at the time of​ incurrence, or b. at the time the finished units to which the fixed overhead relates are sold. A. Absorption costing uses​ (a) and variable costing uses​ (b). B. Variable costing uses​ (a) and absorption costing uses​ (b). C. Variable costing uses​ (a) and absorption costing uses neither. D. Absorption costing uses​ (a) and variable costing uses neither.