At a price of $5 the profit-maximizing output for a perfectly competitive firm is 1,000 units per

Question:

At a price of $5 the profit-maximizing output for a perfectly competitive firm is 1,000 units per year. If the average total cost is $3 per unit, what will be the firm’s profit? If the average total cost is $6 per unit, what will be the firm’s profit?
What is the relationship between profit, price, and average total cost?