问题：Last month, when a company had an opening inventory of 16,500 units and a closing inventory of 18,000 units, the profit using absorption costing was $40,000. The fixed production overhead rate was $10 per unit.
　　What would the profit for last month have been using marginal costing?
　　A. $25,000
　　B. $65,000
　　C. $15,000
　　D. $55,000
　　答案：The correct answer is:$25,000
　　Increase in inventory  = (18,000 - 16,500) units
　　                                        = 1,500 units
　　Difference in profit       = 1,500 units × $10
　　                                        =  $15,000
　　Profits under marginal costing will be $15,000 less than profits under absorption costing ie $40,000 - $15,000 = $25,000.