In an alkalinity titration of a 100.0 mL sample of water from a hot spring, 2.56 mL of a 0.0320 M solution of HCl is needed to reach the first...

In an alkalinity titration of a 100.0 mL sample of water from a hot spring, 2.56 mL of a 0.0320 M  solution of HCl is needed to reach the first equivalence point (pH = 8.3) and another 10.42 mL is needed to reach the second equivalence point (pH = 4.0). If the alkalinity of the spring water is due only to the presence of carbonate and bicarbonate, what are the concentrations of each of them?

(on a side note what does the equivalence points indicate?)