5000 kg/hr of water will be heated from 20o C to35o C by hot water at 140oC A 15o C hot water temperature drop isallowed. A number of double-pipe heat exchangers with annuli and pipes, each connected in series, will be used. Hot water flows through the inner tube. The thermal conductivity of the material is 50 W/m * K Fouling factors: Ri = 0.000176 m2 * K/W Ro= 0.000352 m2 * K/W Inner tube diameters: ID = 0.0525m, OD = 0.0603m Annulus diameters: ID = 0.0779m, OD = 0.0889m. The heat transfer coefficients in the inner tube and in the annulus are 4620 W/m2 * K and 1600 W/m2 * K respectively. Calculate the overall heat transfer coefficient and the surface area of the heat exchanger.