Based on the description of the graphs, let's analyze the situation where the firm can maintain its optimal (least cost) output.

Figure A:

• The horizontal axis represents quantity, and the vertical axis represents price.
• Three demand curves (D₁, D₂, D₃) are shown, which fall from top to bottom.
• A vertical line is drawn at Q₁, and this line intersects all three demand curves at points on the price axis.
• The dashed horizontal lines from P₁, P₂, and P₃ correspond to points of intersection with D₁, D₂, and D₃.

Figure B:

• The horizontal axis represents quantity, and the vertical axis represents price.
• The demand curves (D₃, D₂, D₁) fall from top to bottom, with D₃ at the top.
• The demand curves intersect a single horizontal line at three different points, corresponding to Q₁, Q₂, and Q₃.

Interpretation:

• Optimal (least cost) output is usually the point where the firm produces at a price and quantity level that minimizes costs and maximizes efficiency, typically found where the demand curve intersects the marginal cost curve.

In Figure A, the demand curves are shown as parallel lines falling from top to bottom. The intersection of the vertical line at Q₁ with each of the demand curves suggests a relationship where price is decreasing as quantity increases. This may imply that the firm is adjusting its output level in line with its cost and demand relationships.

In Figure B, the demand curves intersect a horizontal line, suggesting that there is a specific price point at which multiple quantities may meet. However, this does not clearly indicate the firm's ability to achieve optimal output, as it's hard to determine if the firm is achieving the least cost output based on this graph alone.

Conclusion:

Figure A likely represents a situation where the firm can maintain its optimal output, as the vertical line and intersecting demand curves suggest varying prices for a fixed output level. Figure B does not provide enough information to conclude the firm’s optimal output.

Therefore, the correct answer is:

A only.

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Would you like more details on this analysis? Let me know if you have any further questions! Here are some related questions:

1. What is the concept of "least cost output" in economics?
2. How does the intersection of the demand curve and marginal cost curve determine the optimal output?
3. What role do supply and demand curves play in determining the firm's pricing strategy?
4. How can changes in demand curves affect a firm's output decision?
5. What is the relationship between price elasticity of demand and firm output?

Tip: When analyzing graphs like these, pay attention to the intersection points between quantity and price to determine the optimal level of output for the firm.