In the Average Revenue curve for a firm in perfect competition the average revenue is equal to the price of the commodity at all units of output sold.This is because the average revenue is equal to total revenue/output. When we are talking about perfect competition the price is always constant. So we can write revenue as price*output and the output cancels out. So the average revenue is equal to the price.Is this true at 0 units of output sold? How does it make sense that the average revenue exists at zero units of output sold. The reference is to the question asked above.