Supply, Demand, and Equilibrium Price in the Market for Raspberries

No single raspberry farm is big enough to move the market price. The price is set where market supply meets market demand, here at $4.00 and 800 packs. That price is what appears as the flat marginal revenue line in the farm's own diagram.

The slider shifts market demand. A shift changes the equilibrium price, and every farm in the market then faces a new horizontal marginal revenue line.