The following data are from the accounting records of Niles Castings for year 2. Units produced and sold 88,000 Total revenues and costs Sales revenue $290,000 Direct materials costs 60,000 Direct labor costs 31,000 Variable manufacturing overhead 13,000 Fixed manufacturing overhead 46,000 Variable marketing and administrative costs 15,000 Fixed marketing and administrative costs 36,000 Required: a. Prepare a gross margin income statement. b. Prepare a contribution margin income statement.