\text { What is the } K_{s p} \text { equation for } \mathrm{Mg}_{3}\left(\mathrm{PO}_{4}\right)_{2} ? \mathrm{K}_{\mathrm{sp}}=\left[\mathrm{Mg}^{2+}\right]^{2}\left[\mathrm{PO}_{4}{ }^{3-}\right]^{3} \mathrm{K}_{\mathrm{sp}}=\left[\mathrm{Mg}^{2+}\right]^{3}\left[\mathrm{PO}_{4}{ }^{3-}\right]^{2} \mathrm{K}_{\mathrm{cn}}=\left[\mathrm{Mg}^{2+}\right]^{3}\left[\mathrm{PO}_{4}{ }^{3-}\right]^{2} /\left[\mathrm{Mg}_{3}\left(\mathrm{PO}_{4}\right)_{2}\right] \mathrm{K}_{\mathrm{sp}}=\left[\mathrm{Mg}^{2+}\right]\left[\mathrm{PO}_{4}{ }^{3-}\right] \mathrm{K}_{\mathrm{sp}}=3\left[\mathrm{Mg}^{2+}\right]+2\left[\mathrm{PO}_{4}{ }^{3-}\right]