A profit-maximizing firm in a competitive market is currently producing 100 units of output

A profit-maximizing firm in a competitive market is currently producing 100 units of output. It has average revenue of $10, average total cost of $8, and fixed costs of $200.

a. What is its profit?
b. What is its marginal cost?
c. What is its average variable cost?
d. Is the efficient scale of the firm more than, less than, or exactly 100 units?