The level of inventory of a manufactured product has increased by 7,543 units during a period. The following data are also available: Variable Fixed Unit manufacturing costs of the period $13.00 $8.00 Unit operating expenses of the period 4.00 2.00 The effect on operating income if variable costing is used rather than absorption costing would be a(n) Oa. $60,344 increase b. 560,344 decrease c. $75.430 increase d. $75,430 decrease