Under the Basel III Fundamental Review of the Trading Book (FRTB), a bank must calculate Expected Shortfall (ES) at the 97.5% confidence level instead of VaR at 99%. For a normally distributed portfolio with a daily standard deviation of $4.2 million, what is the 1-day ES at 97.5%? (Use z-values: z_0.975 = 1.96; for ES at 97.5% under normality, the multiplier is approximately 2.338.)