Under perfect competition, the average revenue, marginal revenue and price are shown:

Under perfect competition the demand curve ( AR curve) which an individual seller has to face is perfectly elastic and parallel to xaxis .The individual producer is unable to effect the market price and so he is a price taker. He supplies the unlimited quantity of product at prevailing price. Hence MR equals the price of the product and AR is also equal to MR. So MR = AR = P. These three curves are coincide and always shown by a single curve which is perfectly elastic and parallel to the x-axis.}