The correct option is C - 0.741 V
We cannot add the electrode potentials directly because they are an intensive property. Think about density and temperature for example. You cannot just add the density of a rock and a paper directly to get the final density.
Gibb’s energy on the other hand, is an extensive property. We can add it directly.
Adding the first two reactions, we get the third equation and using the free energy concept, we have
(n = number of electrons involved)