On the basis of the following E^o values, the strongest oxidizing agent is
[Fe(CN)₆]^4$$-$$ $$ \to $$ [Fe(CN)₆]^3$$-$$ + e^$$-$$;  E^o = $$-$$0.35 V

Fe²⁺ $$ \to $$ Fe³⁺ + e^$$-$$;  E^o = $$-$$0.77 V

The efficiency of a fuel cell is given by

The equilibrium constant of the reaction:
Cu_(s) + 2Ag⁺_(aq) $$ \to $$ Cu²⁺_(aq) + 2Ag_(s);
E^o = 0.46 V at 298 K is

E^o_Fe²⁺/Fe = $$-$$ 0.441 V and E^o_{Fe³⁺/Fe²⁺} = 0.771 V, the standard EMF of the reaction Fe + 2Fe³⁺ $$ \to $$ 3Fe²⁺ will be