At T(K) in a saturated solution of MgCO$_3$ and Ag$_2$CO$_3$, if the concentration of Mg$^{2+}$ ion is $3.2\times10^{-5}$ M, then the concentration of Ag$^+$ ion in the solution will be [Given: $K_{sp}(MgCO_3)=1.6\times10^{-6}$ and $K_{sp}(Ag_2CO_3)=8.0\times10^{-12}$ at T(K)]