A Na2CO3 standard solution is prepared by transferring 2.4817 g of primary standard-grade sodium carbonate (fw = 106 g/mol) to a 250-ml volumetric flask. Dissolving the sample in - 100 mL distilled water and diluted to the mark. A 25.0 mL aliquot is taken and titrated with 42.65 mL of HCl, calculate the concentration of the HCl solution?