Answer:
Cy and Di
Explanation:
We cannot tell exactly where the right end of the mirror is, but if we assume it is short of allowing Ed and Fred to see each other, we have the following:
Cy can see Cy and everyone to the right
Fred can see Di and everyone to the left
The only two that can see all of Cy, Di, Ed, and Fred are Cy and Di.
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If the mirror extends far enough to the right for Ed to see Fred, then all of Cy, Di, and Ed can see the four folks of interest.
