.Cold water (Cp = 4180 J/kg. °C) enters the tubes of a heat exchanger with 2-shell passe sand 20-tube passes at 20°C at a rate of 3 kg/s,while hot oil (Cp = 2200 J/kg °C) enters the shell at 130°C at the same mass flow rate and leaves at 60°C. If the overall heat transfer coefficient based on the outer surface of the tube is 300 W/m² . °C, determine: a. The rate of heat transfer and b. The heat transfer surface area on the outer-side of the tube.(7 marks)