  The time dependence of the currency exchange rate K treated as a function of
national dividend, investments and difference between total demand for a goods
and supply is considered. To do this a proposed earlier general algorithm of
economic processes describing on the basis of the equations for K like the
equations of statistical physics of open systems is used. A number of
differential equations (including nonlinear ones too) determining the time
dependence of the exchange rate (including oscillations) is obtained.
