Demmurage charges paid to railway for bringing coal to thermal power station?

coal is purchased by the thermal power generation company for the purpose of producing the electricity. coal cost is paid to the coal company. freight charges paid to the railway company. when the railway company supply rakes there may be some delay for the power company to unload the rakes of coal in such cases the railway company impose demmurages for the delay payable by the power company to the railway for the delay in unloading. whether this demmerages paid to railway company to be treated under seperate head or included in the freight charges