Walsh Corporation, which has only one product, has provided the following data concerning its most recent month of operations: Selling price $ 118 Units in beginning inventory 400 Units produced 2,100 Units sold 2,300 Units in ending inventory 200 Variable costs per unit: Direct materials Direct labor Variable manufacturing overhead $ 37 $ 23 $ 3 5 Variable selling and administrative expense $ Fixed costs: Fixed manufacturing overhead $ 73,500 Fixed selling and administrative expense $ 29,900 Variable costs per unit: Direct materials Direct labor Variable manufacturing overhead $ 23 $ 3 5 Variable selling and administrative expense $ Fixed costs: Fixed manufacturing overhead $ 73,500 Fixed selling and administrative expense $ 29,900 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. What is the net operating income for the month under variable costing? Select one: O a. $11,600 O b. $4,600 Oc. $7,000 O d. $24,200