Answer: A) Is the minimum amount a firm must receive to engage in trade.
Explanation: Is a concept based on the law of supply and demand, and is the conditional benefit they obtain form the sale of their products, since they are able to sell them at a higher price than they would be willing to charge. In other words, the difference between the amount that a producer receives from the sale of a good and the lowest amount that the producer is willing to accept for the product. The greater the difference between the two prices, the greater the benefit to the producer.