An adiabatic heat exchangeris used to heat cold water at $$15^\circ$$ C entering at a rate of 5 kg/s by hot air at $$90^\circ$$ C entering also at rate of 5 kg/s If the exit temperature of hot air is $$20^\circ$$ C, the exit temperature of cold water is

A

$$27^\circ$$ C

B

$$32^\circ$$ C

C

$$52^\circ$$ C

D

$$85^\circ$$ C