89. Solving a chemistry problem

2. An excess of KI solution was added to 40.0 cm3 of KMnO4 solution (1.0 cm3 of KMnO4 solution is equivalent to 0.0050 g of iron) and the released iodine was titrated with 35.9 cm3 of Na2S2O3 solution. Calculate the copper titer of Na2S2O3 solution.