b 41. DJH Company produces 1,000 units of Part K per month. The total manufacturing costs of the part are as follows: Direct materials $10,000 Direct labor 15,000 Variable overhead 5,000 Fixed overhead 30,000 Total manufacturing cost $60,000 An outside supplier has offered to supply the part at $40 per unit- It is estimated that 20% of the fixed overhead assigned to Fart X will no longer be incurred if the company purchases the part from the outside supplier. If DJH Company purchases 1,000 units of Part X from the outside supplier per month, then its monthly operating income will a. decrease by $20,000. b decrease by $4,000. c. not change. d increase by $20,000