costing

Participant
ABC organisation Purchase the Scrap of Electronic material i.e Monitor, Keyboards, Printer, Calculator, CPU etc. these Scrap are import from foreign country and purchase complete ship on weight basis and after it all these scrap are recycle i.e crash all these material for obtaining Aluminium, plastic and some other material to sale into the market. my question how to cost these material if we purchase on weight basis how to allocate cost to the materials separately and after recycle of material e.g if printer are crash and we obtain aluminium and plastic so how to allocate cost to Aluminium and plastic. need some reasonable answer.