Alfred Isaac Company, which has only one product, has provided the following data concerning its most recent month of operations: Selling price...... $140 Units in beginning inventory Units produced. Units sold Units in ending inventory.. 300 4,300 4,500 100 Variable costs per unit: Direct materials Direct labor Variable manufacturing overhead ... Variable selling and administrative . $25 $51 $7 $6 Fixed costs: Fixed manufacturing overhead. Fixed selling and administrative...... $150,500 $72,000 The company produces the same number of units every month, although the sales in units vary from month to month. The company's variable costs per unit and total fixed costs have been constant from month to month. Required: a. Prepare an income statement for the month using the contribution format and the variable costing method. b. Prepare an income statement for the month using the absorption costing method. c. Explain the reason of the difference between net operating income figures according to each method. d. Under which circumstances, net operating income figures according to each method will be equal