The level of inventory of a manufactured product has increased by 7,979 units during a period. The following data are also available:

Line Item Description	Variable	Fixed
Unit manufacturing costs of the period	$13.00	$8.00
Unit operating expenses of the period	2.00	2.00

The effect on operating income if variable costing is used rather than absorption costing would be a(n)

a. $63,832 increase

b. $79,790 increase

c. $63,832 decrease

d. $79,790 decrease