Hot water (0.01 m3 /min) enters the tube side of a counter current shell and tube heat exchanger at 80 C and leaves at 50 C. Cold oil (0.05 m3/min) of density 800 kg/m3 and specific heat of 2 kJ/kg.K enters at 20 C. The log mean temperature difference in C is approximately

• A. 32
• B. 37
• C. 45
• D. 50