A fuel gas containing methane and ethane is burned with air in a furnace, producing a stack gas at 300°C and 105 kPa (absolute). You analyze the stack gas and find that it contains no unburned hydrocarbons, oxygen, or carbon monoxide. You also determine the dew-point temperature. 

(a) Estimate the range of possible dew-point temperatures by determining the dew points when the feed is either pure methane or pure ethane. 

(b) Estimate the fraction of the feed that is methane if the measured dew-point temperature is 59.5°C. 

(c) What range of measured dew point temperatures would lead to calculated methane mole fractions within 5% of the value determined in Part (b)?