operating leverage. natural bodyworks (nb) produces the popular ab stretcher that they sell for $200 per unit. nb’s total fixed costs (fixed operating costs depreciation) for the ab stretcher are $200,000.their variable costs are $30 per unit. they are financed entirely by equity and face a 21% corporate tax rate. if sales increase from 4,000 units to 5,000 units, what is the percentage increase in noi