Which expression represents the cell potential $(E_{cell})$?

If $E^{\circ}_{Fe^{2+}/Fe} = -0.440 \ V$ and $E^{\circ}_{Fe^{3+}/Fe^{2+}} = 0.770 \ V$,then $E^{\circ}_{Fe^{3+}/Fe}$ is (in $V$)

Calculate $E^o_{cell}$ for the following cell in $V$:
$Zn_{(s)} | Zn^{2+}_{(aq.)} || Ag^{+}_{(aq.)} | Ag_{(s)}$
Given: $E^o_{Zn^{2+}/Zn} = -0.76 \ V$ ; $E^o_{Ag^{+}/Ag} = 0.80 \ V$

$Mg^{2+}$ displaces hydrogen from acids but copper does not. $A$ galvanic cell prepared by combining $Cu/Cu^{2+}$ and $Mg/Mg^{2+}$ has an $EMF$ of $2.71 \ V$ at $298 \ K$. If the potential of copper electrode is $0.34 \ V$,what is the reduction potential of $Mg$ electrode?

Given:
$E^o_{Cr^{3+}/Cr} = -0.74 \ V$,$E^o_{MnO_4^-/Mn^{2+}} = 1.51 \ V$
$E^o_{Cr_2O_7^{2-}/Cr^{3+}} = 1.33 \ V$,$E^o_{Cl_2/Cl^{-}} = 1.36 \ V$
Based on the data given above,the strongest oxidising agent will be:

The standard reduction potential for $Fe^{2+}/Fe$ and $Sn^{2+}/Sn$ electrodes are $-0.44 \ V$ and $-0.14 \ V$ respectively. For the cell reaction,$Fe^{2+} + Sn \longrightarrow Fe + Sn^{2+}$,the standard emf is: