In a parallel flow heat exchanger, hot fluid enters the heat exchanger at a temperature of 150°C and a mass flow rate of 3 kg/s. The cooling medium enters the heat exchanger at a temperature of 30°C with a mass flow rate of 0.5 kg/s and leaves at a temperature of 70°C. The specific heat capacities of the hot and cold fluids are 1150 J/kg·K and 4180 J/kg·K, respectively. The convection heat transfer coefficient on the inner and outer side of the tube is 300 W/m²·K and 800 W/m²·K, respectively. For a fouling factor of 0.0003 m²·K/W on the tube side and 0.0001 m²·K/W on the shell side, determine

(a) The overall heat transfer coefficient,

(b) The exit temperature of the hot fluid

(c) Surface area of the heat exchanger.