25cm^3 of a solution of BaCl2 is placed in a beaker and Ba2+ ions quantitatively(completely) precipitated by boiling excess NaCO3 solution containing 0.0005moles. After filtration, the remaining NaCO3 solution needed 0.004moles of H Cl for neutralization. Calculate the number of moles of NaCO3 remaining after filtration., therefore deduce the number of moles of BaCl2 which reacted with the NaCO3 solution.