Ethylene glycol is used as an automobile antifreeze and in the manufacture of polyester fibers. The name glycol stems from the sweet taste of this poisonous compound. Combustion of 6.38 mg of ethylene glycol gives 9.06 mg CO2 and 5.58 mg H2O. The compound contains only C, H, and O. What are the mass percentages of the elements in ethylene glycol?