A water sample contains $60.0\mathrm{mg}$ of $\mathrm{Ca}{}^{2+}$ and $24.0\mathrm{mg}$ of $\mathrm{Mg}{}^{2+}$ per litre ($\mathrm{Ca}=40$, $\mathrm{Mg}=24$, $\mathrm{CaCO}{}_3=100$). A $100.0\mathrm{mL}$ portion is titrated with $0.0100\mathrm{M}$ EDTA. At pH 10 both ions react; at pH 12, $\mathrm{Mg}(\mathrm{OH}){}_2$ precipitates and only $\mathrm{Ca}{}^{2+}$ reacts. Which statements are correct?

1. ATotal hardness is $250\mathrm{ppm}$ as $\mathrm{CaCO}{}_3$.
2. BThe hardness due to $\mathrm{Mg}{}^{2+}$ is $100\mathrm{ppm}$ as $\mathrm{CaCO}{}_3$.
3. CThe $\mathrm{Ca}{}^{2+}$ accounts for 40\% of the total hardness.
4. DAt pH 12 the EDTA volume needed for the $100.0\mathrm{mL}$ portion is $15.0\mathrm{mL}$.