A counter flow, concentric tube heat exchanger used for engine cooling has been in service for an extended period of time. The heat transfer surface area of the exchanger is 5 m², and the design value of the overall convection coefficient is 38 W/m² ∙ K. During a test run, engine oil flowing at 0.1 kg/s is cooled from 110°C to 66°C by water supplied at a temperature of 25°C and a flow rate of 0.2 kg/so Determine whether fouling has occurred during the service period. If so calculate the fouling factor, R''_f (m² ∙ K/W).