A mixture of 75.0 mol% propane and 25.0 mol% hydrogen is burned with 25% excess air. Fractional conversions of 90.0% of the propane and 85.0% of the hydrogen are achieved; of the propane that reacts, 95.0% reacts to form CO2 and the balance reacts to form CO. The hot combustion product passes through a boiler in which heat transferred from the gas converts boiler feedwater into steam. Calculate the concentration of CO (ppm on molar basis) in the stack gas