5 Use the following information to answer the following 3 questions: Spark Design Corporation had the following results last month: $ % Sales (15,000 units) 1,500,000 100 Variable expenses 900.000 60 Contribution margin 600.000 40 Fixed expenses 500.000 Operating income 100,000 if sales increase by $100.000 next month. by how much should operating income increase? Select one a $640.000 b 51,600.000 c5100,000 d. $40,000