Approximately how many molecules of ATP are produced from the complete oxidation of one molecule of glucose (C₆H₁₂O₆) through the process of aerobic cellular respiration?

Through the first three stages of cellular respiration only 4 ATP molecules have been produced from the initial glucose molecule. In which of the products of these stages is the potential energy to produce more ATP molecules stored?

Water is one of the products of aerobic cellular respiration. What is the source of the oxygen atom utilized to create the water molecules?