Hot exhaust gases are used in a finned-tube cross-flow heat exchanger to heat 2.5 kg/s of water from 35 to 85 °C. The gases ????p =1.09 kJ/kg ·°C enter at 200 °C and leave at 93 °C. The overall heat- transfer coefficient is 180W/m2·°C. Calculate the area of the heat exchanger using (a) the LMTD approach and (b) the effectiveness-NTU method.