Explanation

Expected Shortfall (ES) at the 97.5% confidence level represents the average of the worst 2.5% of losses. Without the complete context of the distribution or historical data, we cannot definitively determine the exact ES value. However, based on typical ES calculations and the options provided:

• Option A (JPY 398 million) appears to be the most reasonable estimate for a daily ES at 97.5% confidence level
• ES is typically higher than VaR at the same confidence level but should be a realistic estimate of average tail losses
• The other options (JPY 400M, JPY 405M, JPY 497M) may represent different risk measures or confidence levels

Note: To properly calculate ES at 97.5% confidence level, we would need:

• Historical return data or loss distribution
• The ability to identify the worst 2.5% of observations
• Calculate the average of those worst-case scenarios

Since the full context is not provided, this answer is based on the most plausible selection from the given options.