Introduction:
When preparing for the Economics Optional paper in the UPSC exam, case studies can be a valuable tool for understanding real-world applications of economic theories and concepts. However, the decision to aim for a fixed number of case studies per week should be based on various factors and individual preferences.

Factors to consider:
1. Time availability: Before determining a fixed number of case studies, evaluate how much time you can dedicate to your Economics Optional preparation. Consider your other commitments and responsibilities to ensure that you can realistically complete the targeted number of case studies within the given timeframe.

2. Complexity of case studies: Case studies can vary in terms of complexity and length. Some case studies may require more in-depth analysis and research, while others may be relatively simpler. Take into account the difficulty level of the case studies you plan to study and allocate sufficient time accordingly.

3. Quality over quantity: While completing a fixed number of case studies per week may provide a sense of accomplishment, it is important to prioritize quality over quantity. Spending more time understanding and analyzing a few well-chosen case studies can be more beneficial than rushing through a large number of case studies without truly grasping the underlying concepts.

4. Comprehension and retention: Economics Optional requires a deep understanding of economic theories and their practical application. Rushing through multiple case studies within a short period may limit your ability to comprehend and retain the information effectively. It is crucial to give yourself enough time to fully absorb the content of each case study.

Best approach:
Instead of focusing on a fixed number of case studies, it is advisable to adopt a more flexible and personalized approach. Consider the following guidelines:

1. Set realistic goals: Determine a reasonable number of case studies you can comfortably complete within a week, considering your time availability and the complexity of the case studies.

2. Emphasize understanding: Prioritize understanding the key economic concepts and theories discussed in each case study. Take the time to analyze the data, identify relevant economic principles, and evaluate the outcomes.

3. Focus on application: Pay attention to the practical application of economic theories in the case studies. Consider the implications, limitations, and potential policy recommendations that arise from the given scenarios.

4. Supplement with other resources: While case studies are valuable, they should be supplemented with textbooks, reference materials, and other resources to gain a comprehensive understanding of the subject.

5. Regular revision: Allocate time for regular revision of previously studied case studies to reinforce your understanding and improve retention.

Remember, the quality of your preparation matters more than the quantity of case studies completed. Focus on developing a strong conceptual foundation and an analytical approach to economic problem-solving.