Five liters of liquid n-hexane and 4 liters of liquid n-heptanes are mixed and burned with 4000 gram- moles of air. Not all of the hydrocarbons are burned in the furnace, and both CO and CO₂ are formed. If it is possible to do so without additional information, calculate the percent excess air supplied to the furnace: if more information is needed, state what it is and outline the calculation of the percent excess air.