(a) "relevant page" means Telerate screen page 3750 for the display of London Interbank Offered Rates for Dollars (or, if such page or such service shall cease to be available, such other page or such other service (as the case may be) for the purpose of displaying London Interbank Offered Rates for such currency as is then in operation and is customarily used in sub titution for the Telerate screen page 3750 by prime banks in London for determining interbank interest rates); and