The level of inventory of a manufactured product has increased by 8,379 units during a period. The following data are also available: Variable Fixed Unit manufacturing costs of the period $11.00 $4.00 3.00 5.00 Unit operating expenses of the period The effect on operating income if variable costing is used rather than absorption costing would be a(n) Oa. $33,516 increase Ob. $75,411 increase Oc. $75,411 decrease $33,516 decrease