A heat exchanger is used to heat cold water at 15C entering at a rate of 2

Question:

A heat exchanger is used to heat cold water at 15°C entering at a rate of 2 kg/s by hot air at 100°C entering at a rate of 3 kg/s. The heat exchanger is not insulated and is losing heat at a rate of 40 kJ/s. If the exit temperature of hot air is 20°C, the exit temperature of cold water is
(a) 44°C (d) 72°C
(b) 49°C (e) 95°C
(c) 39°C