Letter to Hon. Jerome Powell, Chairman of the Board of Governors of the Federal Reserve; Hon. Randal Quarles, Vice Chairman for Supervision of the Board of Governors of the Federal Reserve; Hon. Blake Paulson, Acting Comptroller of the Currency; and Hon. Jelena McWilliams, Chairman of Federal Deposit Insurance Corporation - Warren and Brown to Regulators: It Would Be a Grave Error to Extend Capital Exemptions for the Nation's Large Banks and Holding Companies