A double pipe counter flow heat exchanger is to be designed to cool 12000 kg/hr of an oil of specific het 1.95 kJ/kgK from 850C to 550C by water entering the heat exchanger at 300C and leaving at 450C. If the OHTC of heat exchanger is 400 W/m2K. Calculate the LMTD and he surface area of the heat exchanger.