Is the reduced form of cytochrome c more likely to give up its electron to oxidized cytochrome a or cytochrome b, why? provide a brief rationale for your answer.

The reduced form of cytochrome c more likely to give up its electron to oxidized cytochrome a having a higher reduction potential.  

Explanation:

Electrons from NADH and FADH2 flow spontaneously from one electron carrier of the electron transport chain to the other. This occurs since the proteins of the ETC are present in the order of increasing reduction potential. The reduced cytochrome b has lower reduction potential than cytochrome c1 which in turn has a lower reduction potential than the cytochrome c.

Cytochrome c is a soluble protein and its single heme accepts an electron from cytochrome b of the Complex III. Now, cytochrome c moves to complex IV which has higher reduction potential and donates the electron to cytochrome a which in turn passes the electrons to O2 via cytochrome a3.

the endomembrane system i think