S1:          Payment for imports and exports is made through a system called foreign exchange. P :           The value of the money of one country in relation to the money of other countries is agreed upon. Q :          These rates of exchange vary from time to time. R :          For instance, an American dollar or a British pound sterling is worth certain amounts in the money of other countries. S :           Sometimes a United States dollar is worth 12 pesos in Mexico. S6:          Another time it may be worth eight pesos. The Proper sequence should be: