The following data are from the accounting records of Niles Castings for year 2. Units produced and sold 81,000 Total revenues and costs Sales revenue $ 310,000 Direct materials costs 67,000 Direct labor costs 40,000 Variable manufacturing overhead 13,000 Fixed manufacturing overhead 40,000 Variable marketing and administrative costs 16,000 Fixed marketing and administrative costs 34,000 Required: a. Prepare a gross margin income statement. b. Prepare a contribution margin income statement.