5–191 (Heat Exchanger) An adiabatic heat exchanger is used to heat cold water at 15°C entering at a rate of 5kg/s with hot air at 90°C entering also at a

rate of 5 kg/s. If the exit temperature of hot air is 20°C, the exit temperature of cold water is (a) 27°C (b) 32°C (c) 52°C (d) 85°C (e) 90°C