The HKD hit the weak-side convertibility undertaking, prompting the Hong Kong Monetary Authority (HKMA) to purchase HKD equivalent to HK$9.42 billion last Thursday (26th), and again this morning (2nd) during the New York session, selling US$2.55 billion (approximately HK$20.018 billion) at the rate of 7.85 per USD.The aggregate balance of the Hong Kong banking system will decrease by HK$20.018 billion to HK$144.175 billion tomorrow (3rd).