Please help- I am stumped.

"A Company has a fixed cost of $20,000 and a production cost of $8 for each unit it manufactures. A unit sells for $10."

a) What is the cost function?

b) What is the revenue function?

c) What is the profit function?

d) Compute the profit (loss) corresponding to production levels of 7,000, 9,000 and 12,000 units, respectively.

Thanks so much