3. The components of marginal revenue Darnell's Fire Engines is the sole seller of fire engines in the fictional country of Pyrotania. Initially, Darnell produced seven fire engines, but he has decided to increase production to eight fire engines. The following graph shows the demand curve Darnell faces. As you can see, to sell the additional engine, Darnell must lower his price from $175,000 to $150,000 per fire engine. Note that while Darnell gains revenue from the additional engine he sells, he also loses revenue from the initial seven engines because he sells them all at the lower price. Use the purple rectangle (diamond symbols) to shade the area representing the revenue lost from the initial seven engines by selling at $150,000 rather than $175,000. Then use the green rectangle (triangle symbols) to shade the area representing the revenue gained from selling an additional engine at $150,000. PRICE (Thousands of dollars per fire engine) 250 225 200 Revenue Lost Demand 175 150 Revenue Gained 125 100 75 50 25 ' 4 $ T 10 QUANTITY (Fire engines)