The values of \( \mathrm{K}_{\mathrm{sp}} \) of \( \mathrm{CaCO}_{3...

The values of \( \mathrm{K}_{\mathrm{sp}} \) of \( \mathrm{CaCO}_{3} \) and \( \mathrm{CaC}_{2} \mathrm{O}_{4} \) are \( 4.7 \times 10^{-9} \) and \( 1.3 \times 10^{-9} \) respectively at \( 25^{\circ} \mathrm{C} \). If
\( \mathrm{P} \) the mixture of these two is washed with water, what is the concentration of \( \mathrm{Ca}^{2+} \) ions in water?
(1) \( 7.746 \times 10^{-5} \mathrm{M} \)
(2) \( 5.831 \times 10^{-5} \mathrm{M} \)
(3) \( 6.856 \times 10^{-5} \mathrm{M} \)
(4) \( 3.606 \times 10^{-5} \mathrm{M} \)