Saturated steam at 300°C is used to heat a counter currently flowing stream of methanol vapor from 65°C to 260°C in an adiabatic heat exchanger. The flow rate of the methanol is 6500 standard liters per minute, and the steam condenses and leaves the heat exchanger as liquid water at 90°C. 

(a) Calculate the required flow rate of the entering steam in m³/min. 

(b) Calculate the rate of heat transfer from the water to the methanol (kW). 

(c) Suppose the outlet temperature of the methanol is measured and found to be 240°C instead of the specified value of 260°C. List five possible realistic explanations for the 20°C difference.