Assume that a firm's marginal revenue curve intersects the rising portion of the marginal cost curve at 100 units of output. At this output level, a profit-maximizing firm's total cost is $1,000. If the price of the product is $4 per unit and the firm produces at the profit-maximizing level, the firm will earn an economic profit or loss equal to:

1. -$700.

2. $200.

3. -$1,000.

4. -$400.

5. -$600.