114. Solving a chemistry problem

A sample of ammonium nitrate weighing 1.2500 g was dissolved in water and received 250.0 ml of solution. An excess of formaldehyde solution was added to an aliquot of 10.00 ml, and 5.05 ml of a sodium hydroxide solution with a molar concentration of 0.1015 mol/l was used to titrate the resulting solution. Calculate the mass fraction of ammonium nitrate in the sample in%.