textMX$\text{MX}$ is a sparingly soluble salt that follows the given solubility equilibrium at 298 K: textMX(texts) rightleftharpoons textM^+(textaq) + textX^-(textaq); quad K_textsp = 10^-10$$\text{MX}(\text{s}) \rightleftharpoons \text{M}^+(\text{aq}) + \text{X}^-(\text{aq}); \quad K_{\text{sp}} = 10^{-10}$$ If the standard reduction potential for textM^+(textaq) rightarrow textM(texts)$\text{M}^+(\text{aq}) \rightarrow \text{M}(\text{s})$ is (E_textM^+/textM^ominus) = 0.79 text V$(E_{\text{M}^+/\text{M}}^{\ominus}) = 0.79 \text{ V}$, then the value of the standard reduction potential for the metal/metal insoluble salt electrode E_textX^-/textMX(texts)/textM^ominus$E_{\text{X}^-/\text{MX}(\text{s})/\text{M}}^{\ominus}$ is \_\_\_\_ text mV$\_\_\_\_ \text{ mV}$. (nearest integer) [Given: frac2.303RTF = 0.059 text V$\frac{2.303RT}{F} = 0.059 \text{ V}$]