Q is a solution of HCl containing 0.12 mol.dm^-3. P is a solution of Na2CO3 of unknown concentration. Solution Q was titrated against 25.0cm^3 portions of solution P and an average titre of 26.25cm^3 was obtained. Calculate the concentration of solution P in mol.dm^-3. Na2CO3 +2HCl = 2NaCl +CO2 + H2O.