2 H2Y2- Ca2 Mg2 <-> CaY2- MgY2- 4 H If 40.03 mL of a water sample is titrated to completion with 12.35 mL of a 9.81 x 10-4 M EDTA solution, what is the concentration in molarity (M) for the amount of metal ions (Ca2 and Mg2 ) in this solution? Note that to "titrate to completion" means that the reaction is complete when the end point was observed.