Two  half reactions of an electrochemical cell are given below : 
$$\begin{gathered} Mn{O}_4^{-}\left(aq\right) +8H^{+}\left(aq\right) + 5e^{-}\to M{n}^{2n}\left(aq\right) +4H_{2}O \left(l\right); \\ {E}^{\circ }=+1.51 V \\ S{n}^{2+}\left(aq\right) \to S{n}^{4+}\to +2e^{-}; \\ {E}^{\circ }=-0.51 V \end{gathered}$$

Construct the redox equation from the standard potential of the cell and predict, if the reaction is reactant favoured or product favoured.