For a business that is past break-even, which of the following statements will not be true as a direct consequence of increasing a company's sales volume by 20% over the present level (all three variables held constant)? a. the total contribution margin will increase by 20% b. the fixed cost will remain constant despite the increase in sales level c. operating income (OI) will increase by 20% over the present Ol (operatin income or operating income) d. total variable costs will increase by 20%