36. Solving a chemistry problem

2. A technical preparation of arsenic weighing 1.00 g was dissolved in an alkaline solution and titrated with 20.0 ml of a 0.20 N solution of iodine. After acidifying the titrated solution, an excess of KI was added to it, and the released iodine was titrated with 40.0 ml of a 0.150 N sodium thiosulfate solution. Based on the reversibility of the reaction As(III) I2 ↔ As(V) 2I-, calculate the mass fractions of As2O3 and As2O5 in the sample.