On the basis of the following $\mathrm{E}°$ values, the strongest oxidizing agent is :

${\left[\mathrm{Fe}(\mathrm{CN}{)}_6\right]}^{4-}\to {\left[\mathrm{Fe}(\mathrm{CN}{)}_6\right]}^{3-}+{\mathrm{e}}^{-};\mathrm{E}°=-0.35\mathrm{V}$

${\mathrm{Fe}}^{2+}\to {\mathrm{Fe}}^{3+}+{\mathrm{e}}^{-} \mathrm{E}°=-0.77\mathrm{V}$

Given,

$\text{(i) }{\mathrm{Cu}}^{2+}+2{\mathrm{e}}^{-}⟶\mathrm{Cu}; \mathrm{E}°=0.337 \mathrm{V}$

$\text{(ii) }{\mathrm{Cu}}^{+2}+{\mathrm{e}}^{-}⟶{\mathrm{Cu}}^{+} ; \mathrm{E}°=0.15 \mathrm{V}$

Electro potential, $\mathrm{E}°$ for the reaction

${\mathrm{Cu}}^{+}+{\mathrm{e}}^{-}⟶\mathrm{Cu}$ will be:

Consider the following relations for emf of an electrochemical cell:
(i) emf of cell = (Oxidation potential of anode) - (Reduction potential of cathode)
(ii) emf of cell = (Oxidation potential of anode) + (Reduction potential of cathode)
(iii) emf of cell = (Reduction potential of anode) + (Reduction potential of cathode)
(iv) emf of cell = (Oxidation potential of anode) - (Oxidation potential of cathode)

Which of the above relations are correct?