9. A heat exchanger is used to cool 1 kg/s of water from 60C to 20C using air at 25C. The water flows through the heat exchanger at a rate of 0.05 kg/s and has a specific heat capacity of 4184 J/kgK. The air flows through the heat exchanger at a rate of 2.5 kg/s and has a specific heat capacity of 1005 J/kgK. The overall heat transfer coefficient is 200 W/mK. Determine the surface area required for the heat exchange