144. Solving a chemistry problem

79. To determine the sodium in the wastewater of soda production, a sample of 500.00 ml was taken, then it was evaporated to 100.00 ml and the sodium was determined by the comparison method. The intensity of the standard solution of sodium with a concentration of 0.010 μg / l was equal to 35 units on the scale of the instrument. The intensity of the analyzed solution was equal to 10 units. Determine the concentration of sodium in the wastewater (mg / l)