Consider the flow of engine oil (cp = 2048 j/kg·k) through a thin-walled copper tube at a rate of 0.3 kg/s. the engine oil that enters the copper tube at an inlet temperature of 80°c is to be cooled by cold water (cp = 4180 j/kg·k) flowing at a temperature of 20°c. it is desired to have an exit temperature of the engine oil not greater than 68°c. the individual convective heat transfer coefficients on oil and water sides are 750 w/m2·k and 350 w/m2·k, respectively. a thermocouple probe installed on the downstream side of the cooling water measures a temperature of 46°c for a double-pipe parallel-flow heat exchanger.]