Green Company produces $1,000$ parts per year, which are used in the assembly of one of its products. The unit product cost of these parts is:

Variable Manufacturing Cost

$$12$

Fixed Manufacturing Cost

$$9$

Unit Product Cost

$$21$

The part can be purchased from an outside supplier for $$20$ per unit. If the part is purchased from the outside supplier, two$-$thirds of the fixed manufacturing costs can be eliminated. What will be the annual impact on the company's operating income of buying the part from the outside supplier? $($Do not round intermediate calculations.$)$a$.$

$$5,000$ increase

b$.$

$$2,000$ decrease

c$.$

$$1,000$ decrease

d$.$

$$1,000$ increase