This excerpt taken from the LUX 20-F filed Jun 28, 2006.
Currency of account
(a) Subject to paragraphs (b) to (e) below, the Base Currency is the currency of account and payment for any sum due from an Obligor under any Finance Document.
(b) A repayment of a Loan or Unpaid Sum or a part of a Loan or Unpaid Sum shall be made in the currency in which that Loan or Unpaid Sum is denominated on its due date. For the avoidance of doubt, a Loan advanced in an Optional Currency is denominated in the Optional Currency and not in the Base Currency.
(c) Each payment of interest shall be made in the currency in which the sum in respect of which the interest is payable was denominated when that interest accrued. For the
avoidance of doubt, interest on a Loan in an Optional Currency is payable in the Optional Currency and not in the Base Currency.
(d) Each payment in respect of costs, expenses or Taxes shall be made in the currency in which the costs, expenses or Taxes are incurred.
(e) Any amount expressed to be payable in a currency other than the Base Currency shall be paid in that other currency.