Artikel 13

Wherever it is provided in the present Agreement and the Annexes thereto that an amount shall be calculated on the basis of a rate of exchange, such rate shall, except in the cases provided for in Annex III and in Article 8 of Annex IV of the present Agreement; be
(a) determined by the par values of the currencies concerned in force on the appropriate date as agreed with the International Monetary Fund under Article IV, Section 1, of the Articles of Agreement of the International Monetary Fund; or
(b) if no such par values are or were in force on the appropriate date, the rate of exchange agreed for current payments in a bilateral payments agreement between the Governments concerned or their monetary authorities; or
(c) if neither par values nor rates in bilateral payments agreements are or were in force on the appropriate date, the middle rate of exchange generally applicable for transactions ruling for cable transfers in the currency of the country in which payment is to be made in the principal exchange market of the other country on that date, or on the last date before that date on which such rate was ruling; or
(d) if there is or was no rate of exchange as specified under (a), (b) or (c) at the appropriate date, the cross-rate of exchange resulting from the middle rates of exchange ruling for the currencies in question in the principal exchange market of a third country dealing in those currencies on that date or the last date before the said date upon which such rates were ruling.