Hong Kong exchange fund\'s foreign assets rose 30.8 billion HK dollars (about 3.9 billion U.S. dollars) to 2.3 trillion HK dollars in September, the Hong Kong Monetary Authority said here Friday. The monetary base, comprising certificates of indebtedness, government issued currency notes and coins in circulation, the aggregate balance and exchange fund bills and notes issued, amounted to 1.1 trillion HK dollars. Claims on the private sector in Hong Kong amounted to 118.1 billion HK dollars. Foreign liabilities, representing fees payable to the exchange fund\'s external managers, amounted to 200 million HK dollars.