Question 487775
A and B both agree
If I was telling the truth, then both
A and B were lying.
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But there is no day that both
A and B are lying, since:
A is lying on
Mon, Tues, Wed
B is lying on
Thurs, Fri, Sat
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Therefore, I must have been lying
and both A and B were telling the truth
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There is only 1 day when both A and B
are telling the truth, so today 
must be Sunday