The level of inventory of a manufactured product has increased by 8,428 units during a period. The following data are also available: Variable Fixed Unit manufacturing costs of the period $10.00 $7.00 Unit operating expenses of the period 4.00 4.00 The effect on operating income if variable costing is used rather than absorption costing would be an) a. $92,708 decrease b. $58,996 decrease c. $58,996 increase d. $92,708 increase