A shell-and-tube heat exchanger with a single shell and tube pass is used to cool the oil of a large marine engine. Lake water (the shell-side fluid) enters the heat exchanger at 2 kg/s and 15 degrees Celsius, while the oil enters at 1 kg/s and 140 degrees Celsius. The oil flows through 100 copper tubes, each 500 mm long and having inner and outer diameters of 6 and 8 mm. The shell-side convection coefficient is approximately 500 W/m^2-K. Determine the oil outlet temperature.