1 USD = CNY (6.7010-0.0100)/(6.7040-0.0050) = 6.6910/6.6990.
Hk1= CNY (6.6910/7.8360)/(6.6990/7.8260) = 0.8539/0.8560.
After three months, the exporter's HK$ 6,543,800+RMB 0,000 can be converted into RMB 853,900.