Two fluids, A and B exchange heat in a counter-current heat exchanger. Fluid a enters at 4200C and has a mass flow rate of 1 kg/s. Fluid B enters at 200C and also has a mass flow rate of 1 kg/s, Effectiveness of heat exchanger is 75%. Determine the heat transfer rate and exit temperature of fluid B. (Specific heat of fluid A is 1 kJ/kg K and that of fluid B is 4 kJ/kgK).