Harvey Automobiles Uses a Standard Part in the Manufacture of Several

Harvey Automobiles uses a standard part in the manufacture of several of its trucks.The cost of producing 40,000 parts is $120,000,which includes fixed costs of $60,000 and variable costs of $60,000.The company can buy the part from an outside supplier for $3.00 per unit,and avoid 30% of the fixed costs.
If Harvey Automobiles makes the part,how much will its operating income be?

A) $42,000 greater than if the company bought the part
B) $42,000 less than if the company bought the part
C) $78,000 greater than if the company bought the part
D) $78,000 less than if the company bought the part