Final answer:
Producer surplus in a market economy is the amount that a seller is paid above their minimum acceptable price, across the quantity sold, and is maximized at market equilibrium.
Step-by-step explanation:
In a market economy, producer surplus is equal to the amount by which the market price exceeds the sellers' minimum acceptable prices for their goods, over the quantity sold. It's represented by the area above the supply curve and below the market price, up to the quantity traded.
According to Figure 3.23, if producers were willing to supply at $45 but the equilibrium price is $80, the producer surplus is the amount between these two prices, over the quantity of goods sold. This surplus reflects the extra benefit that producers receive for their products beyond their minimum costs to supply them. Combined with consumer surplus, it creates the social surplus, which is maximized at market equilibrium.