The level of inventory of a manufactured product has increased by 9,288 units during a period. The following data are also available: Variable Fixed $12.00 $8.00 Unit manufacturing costs of the period Unit operating expenses of the period 4.00 1.00 The effect on operating income if absorption costing is used rather than variable costing would be a a. $74,304 increase b. $74,304 decrease c. $83,592 decrease d. $83,592 increase