Z Inc. manufactures a component Zeta which it uses in production of its main product. The manufacturing costs per unit of Zeta are as follows: Direct material Item Cost per unit 3.50 Direct labor 4.50 Variable manufacturing overhead 2.50 2.00 Fixed manufacturing overhead Annual requirement of Zeta is 8,000 units. Fixed manufacturing overhead is allocated to Zeta based on machine-hours used in its production and cannot be avoided if production of Zeta is stopped. An outside supplier has offered Z Inc. to supply 8,000 units at a total cost of $96,000. If Z Inc. purchases the component Zeta from the outside supplier, how will it affect its operating income? a. Operating income will increase by $4,000 b. Operating income will decrease by $4,000 c. Operating income will increase by $6,000 d. Operating income will decrease by $12,000