Example
The inverse supply for bananas is `P = 1 + 2 Q_s`.
If a banana is sold for $5, producers will produce `Q_s = \frac{5 - 1}{2} = 2`.
The Producer Surplus is `\text{PS} = \frac{\left( 5 - 1 \right) \times 2}{2} = \frac{4 \times 2}{2} = $4`.
Question
The supply for bananas is `Q_S = \frac{P - 300}{30}`.
What is the Producer Surplus when the price is $9000?
Step 1: Quantity Supplied
At price $9000, the quantity demanded is `Q_S = \frac{P - 300}{30} = \frac{9000 - 300}{30} = 290`.
Step 2: Inverse Supply
$$ \begin{align*} Q_S &= \frac{P - 300}{30} \\ 30 Q_S &= P - 300 \\ 300 + 30 Q_S &= P \end{align*} $$So the inverse supply curve follows the equation `P = 300 + 30 Q_S`.
Step 3: Draw the graph
Step 4: Calculate the Producer Surplus
`\text{PS} = \frac{(9000 - 300) \times 290}{2} = 1261500.0`