How does a firm determine the optimal input combination using isocost lines and isoquant curves?

• A. By selecting the input combination that maximizes the distance between the isocost line and the isoquant curve.
• B. By finding the point where the isocost line intersects the isoquant curve.
• C. By finding the point where the isocost line is tangent to the highest possible isoquant curve.
• D. By choosing the input combination that lies furthest from the origin on the isocost line.

Answer: (C)