[Joniaguis]

0.476 +/- 0.001 g sample containing (NH₄)₂C₂O₄ (ammonium oxalate) was dissolved in water and made strongly alkaline with KOH, which converted NH₄⁺ to NH₃. The liberated NH₃ was distilled into exactly 50.0 +/- 0.1ml of 0.0504 +/- 0.0001M H₂SO₄. The excess H₂SO₄ was back titrated with 11.3 +/- 0.1ml of 0.1214 +/- 0.0001 ml NaOH.

Calculate:
1) The percent N in the sample.
2) The percent ammonium oxalate in the sample
3) The overall error in the result expressed as percent N

(N=14; C=12; O=16)