If K_c for the reaction

${\mathrm{Cu}}^{2+}\left(\mathrm{aq}\right)+{\mathrm{Sn}}^{2+}\left(\mathrm{aq}\right)⟶{\mathrm{Sn}}^{4+}\left(\mathrm{aq}\right)+\mathrm{Cu}\left(\mathrm{s}\right)$

at 25° C is represented as 2.6 × 10^y then find the value of y. 

$\text{ (Given : }{\mathrm{E}}_{{\mathrm{Cu}}^{2+}\mid \mathrm{Cu}}^{\circ }=0.34\mathrm{V};{\mathrm{E}}_{{\mathrm{Sn}}^{4+}\mid {\mathrm{Sn}}^{2+}}^{\circ }=0.15\mathrm{V}\text{ ) }$