If an irrigation water source has the concentrations of $\mathrm{Na}^{+}$. $\mathrm{Ca}^{+}$ and $\mathrm{Mg}^{+}$ as 28,10 and 5 milliequivalents per litre, respectively, then the Sodium adsorption ratio of this water is____________
If an irrigation water source has the concentrations of $\mathrm{Na}^{+}$. $\mathrm{Ca}^{+}$ and $\mathrm{Mg}^{+}$ as 28,10 and 5 milliequivalents per litre, respectively, then the Sodium adsorption ratio of this water is____________