(a) Statement in United States currency required. All fares and charges shall be stated in cents or dollars of the United States except as provided in paragraph (b) of this section.
(b) Statements in both United States and foreign currencies permitted. Fares and charges applying between points in the United States, on the one hand, and points in foreign countries, on the other hand, or applying between points in foreign countries, may also be stated in the currencies of foreign countries in addition to being stated in United States currency as required by paragraph (a) of this section: Provided, that:
(1) The fares and charges stated in currencies of countries other than the United States are substantially equivalent in value to the respective fares and charges stated in cents or dollars of the United States.
(2) Each record containing fares and charges shall clearly indicate the respective currencies in which the fares and charges thereon are stated, and
(3) The fares and charges stated in cents or dollars of the United States are published separately from those stated in currencies of other countries. This shall be done in a systematic manner and the fares and charges in the respective currencies shall be published in separate records.