Let's solve the problem step by step. ## 1. **Draw the Cost Curves** ### **a. Marginal Cost (MC) Curve** - **Shape:** U-shaped (first decreases, then increases due to diminishing returns). - **Position:** Starts above AVC and ATC at low quantities, intersects both at their minimum points. ### **b. Average Total Cost (ATC) Curve** - **Shape:** U-shaped, always above AVC. - **Position:** Minimum point is above minimum AVC. ### **c. Average Variable Cost (AVC) Curve** - **Shape:** U-shaped, lies below ATC. --- ## 2. **Draw Revenue Curves** Since the firm is **perfectly competitive**, the price (P), average revenue (AR), and marginal revenue (MR) are all **equal and constant** (horizontal line). --- ## 3. **Mark the Profit-Maximizing Output** - The profit-maximizing quantity is where **MC = MR (or P)**. --- ## 4. **Sketch** Here's how you should draw your graph on the provided grid: ``` Price ($) | | ATC | /\ | / \ | P=AR=MR------------------------- (horizontal line above ATC and AVC minimum) | / \ | / \ | / \ | / \ | AVC | / \ |-------/----\----------------------------- Quantity (Q) | | | | AVC ATC ``` - **MC curve:** U-shaped, intersects both AVC and ATC at their minimum points. - **ATC and AVC curves:** Both U-shaped; ATC above AVC. - **P=AR=MR line:** A horizontal line above the minimum points of ATC and AVC. - **Profit-maximizing Q:** Where MC crosses P=MR=AR (vertical dotted line at this Q). --- ## 5. **Label All Curves and Points** - Label the horizontal axis as **Quantity (Q)** and vertical as **Price/Cost ($)**. - Label the curves: **MC**, **ATC**, **AVC**. - Label horizontal line as **P = AR = MR**. - Mark and label the **profit-maximizing quantity**: where **MC = MR**. --- ## 6. **Explanation** - A perfectly competitive firm takes market price as given. - **MR = AR = P** (horizontal). - The profit-maximizing output is where **MC = MR**. - Because price is above minimum ATC, the firm earns a **positive economic profit**. --- ## 7. **Final Answer (Summary)** **The profit-maximizing quantity is where MC = MR = P, which is where the MC curve crosses the horizontal P=MR=AR line above the minimum ATC.** --- ### **Example Graph** (Illustrative drawing for your grid)  *Alt text: Diagram showing MC, ATC, AVC curves with a horizontal P=MR=AR line above the minimum ATC, and the profit-maximizing Q where MC = MR.* --- **You should replicate this on your grid, labeling all curves and the profit-maximizing quantity.**

# Definitions of Cost Concepts ## 1. **Marginal Cost (MC)** The additional cost incurred by producing one more unit of a good, reflecting changes in total cost as output varies. ## 2. **Average Total Cost (ATC)** The total cost per unit produced, calculated by dividing total costs (fixed and variable) by the quantity of output produced. ## 3. **Average Variable Cost (AVC)** The variable cost per unit of output, determined by dividing total variable costs by the quantity produced, excluding fixed costs.