Iron Decor manufactures decorative iron railings. In preparing for next year's operations, management has developed the following estimates: Total $1,000,000 $200,000 $50,000 Per Unit $50.00 $10.00 $2.50 ........ Sales (20,000 units).... Direct materials. Direct labor (variable)... Manufacturing overhead: Variable........... Fixed ............ Selling & administrative: Variable. Fixed ..... $70,000 $80,000 $3.50 $4.00 $100,000 $30,000 $5.00 $1.50 Required: Compute the following items: a. Unit contribution margin. b. Contribution margin ratio. C. Break-even in dollar sales. d. Margin of safety percentage. e. If the sales volume increases by 20% with no change in total fixed expenses, what will be the change in net operating income