(1) An instrument is payable in money if the medium of exchange in which it is payable is money at the time the instrument is made. An instrument payable in "currency" or "current funds" is payable in money.(2) A promise or order to pay a sum stated in a foreign currency is for a sum certain in money and may be satisfied by payment of that number of dollars which the stated foreign currency will purchase at the buying sight rate for that currency on the day on which the instrument is payable, or, if payable on demand, on the day of demand.