Calculate the mass percentage of nitrogen in organic

Question

A. Combustion analysis of a 25.70mg sample of an organic compound containing only C, H, and N yielded 71.49mg of carbon dioxide and 14.64mg of water. Calculate the mass percentage of nitrogen in organic compound?

B. The percentage composition by mass of a compound is 76.0% C,12.8% H, and 11.2% O. The 3 molar mass of this compound is 569g/mol. Determine the molecular and empirical formulas of compound?

  Empirical:           Molecular:

1)C₉H₁₈O             C₉H₁₈O  

2)C₉H₁₈O             C₃₆H₃₂O₄

3)C₉H₁₈O              C₁₈H₃₆O₂

4)C₈H₁₆O₂            C₉H₁₈O  

5)C₈H₁₆O₂            C₁₈H₃₆O₂