0.0350 of potassium sulphate is transferred and weighted to 250 ml volumetric flask , which is then diluted to the mark with distilled water, assume density is 1.000g/ml, the potassium sulphate purity in the water is only 85.5%. if the impurity is consisted of entirely of sodium sulphate, taking this into account, find out the concentration of sulphate in 250ml of solution.