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Empirical formula question

Hey guys can someone help me with the question below..

1.50g of an organic compound containing carbon, hydrogen and oxygen only gave, on complete combustion, 3.41g of carbon dioxide and 1.40g of water. Calculate its empirical formula.

I have done some working out but I'm stuck at the moment but anyway for my working out, I found moles of CO2 (3.41/44 = 0.0775) and moles of H2O ( 1.40/18 = 0.7 recurring). My next step is to divide by the smallest number is gives me a ratio of 1 : 1 What I don't understand is , I know there has to be oxygen in the empirical but how do I work out the moles of the oxygen?