A counterflow double-pipe heat exchanger operates with hot water flowing inside the inner pipe and a polymer fluid flowing in the annular space between the two pipes. The water-flow rate is 2.0 kg/s2.0 kg/s and it enters at a temperature of 90∘C90∘C. The polymer enters at a temperature of 10∘C10∘C and leaves at a temperature of 50∘C50∘C while the water leaves the exchanger at a temperature of 60∘C60∘C. Determine the value of the overall heat-transfer coefficient expressed in W/m2⋅∘CW/m2⋅∘C, if the area for the heat exchanger is 20 m220 m2.