Theory of The Firm – Profit Maximization

Marginal revenue displays the added revenue from each product sold, the reason the line has a negative gradient is the factor that as there is a greater quantity supplied there is a lower price, as the product is less scarce. When marginal revenue crosses the x-axis in a graph it can be noted that every product produced from that point on-wards takes away from revenue.

Through the understanding of the nature of marginal revenue, we can produce a model curve for a firm’s total revenue. It can be noted that the x-intercept of the marginal revenue graph represents the point at which the total revenue graph is at the peak.


Marginal cost displays the added cost from each product sold due to the factors of production being employed such as labour, materials, etc. Marginal cost represents all of the variable costs of the firm, and how there is an increase in cost when more is produced. However, average total cost allows us to see what the firm should actually pay for production.


Average total cost involves the average variable and fixed costs. The curve displayed above is of the average total cost in the short term. The curve is in a negative gradient as long as marginal costs do not exceed the average total cost, the initial negative gradient can be explained as average fixed costs declines as quantity produced increase, as factors such as the factory are becoming more efficient. The reason the gradient increases is because of the greater increase in marginal cost whereas average fixed cost does not radically change to counteract. This is further explained by the law of diminishing marginal returns.

The understanding of average total cost allows us to use the profit maximization point of marginal cost and marginal revenue graph to analyse what the total revenue is and what the total cost is, enabling the actual portion of profit from production.

There are two examples below, the first one display’s firms operating at point of profit making, and the second an example of loss making. Notice the distinct difference between them as the gradient of average revenue or the position of average total cost. As there are a variety of factors present in the positioning and gradients of each curve and line, it is important to look at what are the points to look at for profit maximization The average revenue line is used as it represents the demand curve, and the average total cost curve is used as it represents the operating costs of the term when a given quantity is supplied. This allows revenue to be worked out through price x quantity, where the quantity at profit maximization meets the average revenue line and average total cost curve.

Graphs to be edited




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