The price specified in this contract shall be based upon the present exchange rate (HK $ 5. 65 per U.S.Dollar or HK $10. 50 per Sterling Pound).

In case of variation of such rate by more than 3 per cent after the date of this contract, the price shall be adjusted and settled according to the corresponding change.

As well as claims there are also derivative instruments-contracts relating to the prices of securities, interest rates or foreign exchange rates at some date in the future.