Aircraft products, a manufacturer of aircraft landing gear, makes 1,000 units each year of a special valve used in assembling one of its products. the unit cost of producing this valve includes variable costs of $70 and fixed costs of $60. the valves could be purchased from an outside supplier at $77 each. if the valve were purchased from the outside supplier, 40% of the total fixed costs incurred in producing this valve could be eliminated. buying the valves from the outside supplier instead of making them would cause the company's operating income to: 2.85 points a. increase by $26,000. b. increase by $17,000. c. decrease by $9,000 d. decrease by $29,000