Final answer:
The firm's output is 1,000 units, and its profit is zero, calculated by dividing the total revenue by the average total cost, with profits equalling zero in long run equilibrium.
Step-by-step explanation:
When analyzing scenarios of a perfectly competitive firm, it's important to know that if a firm is in long run equilibrium, its marginal cost (MC) will be equal to its average total cost (ATC) and its price. Since the firm's total revenue (TR) is $100,000 and the average total cost (ATC) is $100, we can find out the output by dividing the total revenue by the ATC. Thus, the firm's output is 1,000 units ($100,000 ÷ $100 = 1,000 units). In the long run equilibrium, price (P) equals ATC, so the firm will make zero economic profit because total revenue will exactly equal total costs (TR = TC).
In this context, the firm's profit is zero, not negative or positive, since it is covering all its costs, including the opportunity costs. This is characteristic of perfectly competitive markets in the long run, where firms earn normal profits but not economic profits.